Is it best practice to send both HTML and Text email?
If I only send HTML what are the dangers?
I'm thinking something like this below, from http://johnnycoder.com/blog/2009/04/15/net-mailmessage-linkedresources-alternateviews-and-exceptions/.
try
{
// Assign a sender, recipient and subject to new mail message
MailAddress sender =
new MailAddress("sender#johnnycoder.com", "Sender");
MailAddress recipient =
new MailAddress("recipient#johnnycoder.com", "Recipient");
MailMessage m = new MailMessage(sender, recipient);
m.Subject = "Test Message";
// Define the plain text alternate view and add to message
string plainTextBody =
"You must use an email client that supports HTML messages";
AlternateView plainTextView =
AlternateView.CreateAlternateViewFromString(
plainTextBody, null, MediaTypeNames.Text.Plain);
m.AlternateViews.Add(plainTextView);
// Define the html alternate view with embedded image and
// add to message. To reference images attached as linked
// resources from your HTML message body, use "cid:contentID"
// in the <img> tag...
string htmlBody =
"<html><body><h1>Picture</h1><br>" +
"<img src=\"cid:SampleImage\"></body></html>";
AlternateView htmlView =
AlternateView.CreateAlternateViewFromString(
htmlBody, null, MediaTypeNames.Text.Html);
// ...and then define the actual LinkedResource matching the
// ContentID property as found in the image tag. In this case,
// the HTML message includes the tag
// <img src=\"cid:SampleImage\"> and the following
// LinkedResource.ContentId is set to "SampleImage"
LinkedResource sampleImage =
new LinkedResource("sample.jpg",
MediaTypeNames.Image.Jpeg);
sampleImage.ContentId = "SampleImage";
htmlView.LinkedResources.Add(sampleImage);
m.AlternateViews.Add(htmlView);
// Finally, configure smtp or alternatively use the
// system.net mailSettings
SmtpClient smtp = new SmtpClient
{
Host = "smtp.example.com",
UseDefaultCredentials = false,
Credentials =
new NetworkCredential("username", "password")
};
//<system.net>
// <mailSettings>
// <smtp deliveryMethod="Network">
// <network host="smtp.example.com"
// port="25" defaultCredentials="true"/>
// </smtp>
// </mailSettings>
//</system.net>
smtp.Send(m);
}
catch (ArgumentException)
{
throw new
ArgumentException("Undefined sender and/or recipient.");
}
catch (FormatException)
{
throw new
FormatException("Invalid sender and/or recipient.");
}
catch (InvalidOperationException)
{
throw new
InvalidOperationException("Undefined SMTP server.");
}
catch (SmtpFailedRecipientException)
{
throw new SmtpFailedRecipientException(
"The mail server says that there is no mailbox for recipient");
}
catch (SmtpException ex)
{
// Invalid hostnames result in a WebException InnerException that
// provides a more descriptive error, so get the base exception
Exception inner = ex.GetBaseException();
throw new SmtpException("Could not send message: " + inner.Message);
}
I would say that, in today's world, the "best-practice" approach would be to ensure that you send your message as both plain text and HTML (if you really want to send HTML email messages).
Oh, and make sure you do actually send the content in the plain text view, rather than a single sentence saying "You must use an email client that supports HTML messages". Google Mail takes this approach, and it seems to work perfectly, allowing "rich" views on full-fledged PC clients, whilst also allowing "minimal" views on more restricted devices (i.e. Mobile/Cell phones).
If you want to take a purist's view, you wouldn't be sending HTML emails at all, nor would you ever "attach" a binary file to an email. Both corruptions of the original email standard, which was only ever originally intended for plain text.
(See some people's opinions of this here and here)
However, in the pragmatic modern-day real world, HTML email is very real, and very acceptable. The primary downside to sending HTML email is whether the recipient will see the email in the way that you intended them to see it. This is much the same problem that web designers have battled with for years; getting their websites to look "just right" in all possible browsers (although it's significantly easier today than it was many years ago).
Similar to ensuring that a website functions correctly without requiring Javascript, by sending your emails as both HTML and Plain Text, you'll ensure that your emails degrade gracefully so that people reading their emails on (for example) small mobile devices (something that's becoming more and more prevalent these days - and which may or may not be capable of rendering a complete HTML email) can still read your email content without issue.
If you only send HTML, then anyone reading email on a text-only device will have trouble.
For example, I suspect many low-end mobile devices are capable of reading email but not displaying full HTML.
I would say it's best practice to either send text-only, or text and HTML.
I don't see why you're catching a bunch of exceptions only to rethrow the same exception type with a different message, by the way - the original message may well be more descriptive.
Another reason to send both is that many mailservers mark emails that only contain HTML content as spam. You don't want all your emails to be put in the junk folder.
I think yes, the best practice is to send both. The reason (c&p from wikipedia):
The default e-mail format according to RFC 2822 is plain text. Thus
e-mail software isn't required to support HTML formatting. Sending
HTML formatted e-mails can therefore lead to problems at the
recipient's end if it's one of those clients that don't support it. In
the worst case, the recipient will see the HTML code instead of the
intended message.
Sharing my experience with sending both HTML and text in one email:
I have created an email message that has 2 views: text and html using C# AlternateView classes.
What did I get?
On Mac, tested on High Sierra:
Apple Mail app was showing the Html. If the order of messages is reversed: Html - text then Apple Mail will show the text view. The conclusion: Apple Mail is using the last view as default.
In Windows, Outlook 2010:
Microsoft Outlook by default is using the Html view. The order of views in the email doesn't matter: html,text; text,html;
If for some reason you selected a setting to show incoming messages as a text then the Html version of your email will be converted into the text by Outlook.
Even so you send the text version of your email (which might be slightly different from the HTML version and was formatted to look pretty) it won't be used.
So you don't need to send the text version of your email if you know that your clients use Outlook and Html version is selected as default.
Mozilla Thunderbird respects your settings and shows the correct Html or text version of your email. It works correctly on Mac and in Windows
Hope it helps
Several email clients will use the last AlternateView that was added to the AlternateViews.
So if you prefer to have your mail displayed as HTML, be sure to add that last.
I have notice this for IOS mail and OSX mail, while Android Email seems to prefer HTML if it is available. I am not sure for which versions this holds, and the behaviour is often user-configurable, but in my experience these were the defaults.
Related
I am working on windows application for email sending.
For text formatting i used tinymce editor for email body.
Used tinymce insert image functionality for adding image in email body but when email is sent to user. Images does not appear in user email body.
Then i tried to add base64 image manually as below:
<img src='data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAOYAAABLCAYAAABk6PuLAAAACXBIWXMAASdHAAEnRwEEDs /'>
Which is failed to load images.
Can we use linked resources and alternate view in tiny mce?
How to load images in email body?
Tiny MCE is just an HTML editor and not a tool which can be used for creating alternate views for email.
Moreover, all email clients don't support inline images (with data URL).
Alternate view is the only way to ensure that all email clients will be able to show your content in the intended manner.
Create a dictionary of linked resources:
Dictionary<string, byte[]> linkedResources = new Dictionary<string, byte[]>();
linkedResources.Add("img1", byte[]);
Create a common method to send email:
public bool SendEmail(Dictionary<string, byte[]> linkedResources)
{
using (SmtpClient mailSender = new SmtpClient("SmtpHost", 22))
{
MailMessage emailMessage = new MailMessage()
{
Subject = "Subject",
SubjectEncoding = Encoding.ASCII,
IsBodyHtml = true,
Body = "Message",
BodyEncoding = Encoding.ASCII,
From = new MailAddress("Sender#domain.com")
};
emailMessage.BodyEncoding = Encoding.ASCII;
emailMessage.IsBodyHtml = true;
AlternateView av = AlternateView.CreateAlternateViewFromString(emailMessage.Body, null, MediaTypeNames.Text.Html);
foreach (var item in linkedResources)
{
MemoryStream streamBitmap = new MemoryStream(item.Value);
var linkedResource = new LinkedResource(streamBitmap, MediaTypeNames.Image.Jpeg);
linkedResource.ContentId = item.Key;
av.LinkedResources.Add(linkedResource);
}
emailMessage.AlternateViews.Add(av);
mailSender.Send(emailMessage);
return true;
}
}
The real question you need to answer is "what is the best way to insert an image in an email". This is a very broad topic that has been answered many times - a little research should lead you to the most common approaches and their pros/cons:
https://sendgrid.com/blog/embedding-images-emails-facts/
https://www.campaignmonitor.com/blog/how-to/2008/08/embedding-images-in-email/
https://www.quora.com/Whats-the-best-practices-for-embedding-images-into-HTML-emails
there is no best solution for that, you can embed the images or attach them as files or just send them as links.
it depends on your requirements. it actually making image tags and link them to my server to get more analytics like the user had opened the email by loading the image throw a handler and the handler receive logs when the user opened the email and I can know how many users opened that email and so on.
Send grid is great for sending emails and getting analytics out of them because it tracks almost everything related to your email, and you should use Send grid to avoid Spam filters
In my experience the only way to solve this is to store that image on the server where it's publicly accessible and then point the img tag src attribute to that url. You have to understand that the HTML that's used in email is severely restricted to regular HTML.
I am writing a system to send out bulk emails to clients and for each site we store an HTML and Text version of the email so that if the users mail client doesn't support HTML the text view is still formatted correctly and as we want.
We don't want to just generate the plain text version from the HTML version as it adds in lots of menu links and other text which isn't formatted as we want.
This works fine in ASP classic with the Persits Email Component = http://www.aspemail.com/
as we add the HTML string as the Body and the text string as the AltBody.
However I am having trouble replicating this in C# .NET 4.5
I have followed as many examples as possible but my method that returns the MailMessage object which needs to pass the HTML looking for images/banners and then replace the URLS with ContentIDs and LinkedResources is somehow returning an email that looks great in HTML and Simple HTML View (in Thunderbird).
However whatever I do the plain text view seems to always be a version of the HTML that the object is trying to convert into text RATHER than the textual string we have pre-formatted and want to use.
If I debug the code I can see that the string is correct before I add it to the alternative view so I don't know what else I need to do.
In my method that parses the HTML, adds linked resources and returns a MailMessage object I have the following code:
<pre>
/* I pass in a custom SiteEmail object with 2 properties HTMLEmail and TextEmail that hold both versions of the email */
public MailMessage ParseEmailImages(SiteEmail siteEmail)
{
MailMessage email = new MailMessage();
// extract the HTML version as we need to parse it to swap URLs for ContentID/Resources and paths etc
string HTML = siteEmail.HTMLEmail;
// this is a generic list to hold all my picture resource objects that I find (swapping image URLs to paths and contentIDs)
List<LinkedResource> pictureResources = new List<LinkedResource>();
// code to find all the paths, create image resource objects and add them to my list - and modify the HTML to reference
// the new ContentIDs I swap the URLs for so the images are embedded in the email
// ..... code .....
// finished finding resource objects build email parts and return to caller
// Add each alternate view to the message.
// add the HTML view using my newly parsed HTML string
ContentType HtmlContentType = new ContentType("text/html; charset=UTF-8");
AlternateView altViewHTML = AlternateView.CreateAlternateViewFromString(HTML, HtmlContentType);
altViewHTML.TransferEncoding = TransferEncoding.QuotedPrintable;
// when I check here the siteEmail.TextEmail holds the CORRECT textual string I want BUT it's not displaying in the sent email
ContentType PlainContentType = new ContentType("text/plain; charset=UTF-8");
// as we didn't need to change anything in the text view we can just reference it straight out my custom email object siteEmail
AlternateView altViewText = AlternateView.CreateAlternateViewFromString(siteEmail.TextEmail, PlainContentType);
altViewText.TransferEncoding = TransferEncoding.QuotedPrintable;
// loop through all my picture resource objects and ensure they are embedded into the HTML email
foreach (LinkedResource pictureResource in pictureResources)
{
pictureResource.TransferEncoding = TransferEncoding.Base64;
altViewHTML.LinkedResources.Add(pictureResource);
}
// add both parts of the email (text/html) which are both alternative views to message
email.AlternateViews.Add(altViewText);
email.AlternateViews.Add(altViewHTML);
// return email object
return email;
}
// a very cut down example of the calling method
public bool SendEmail()
{
// parse our email object
MailMessage EmailMailMessage = this.ParseEmailImages(this.SiteEmail);
// send email
EmailMailMessage.From = new MailAddress(this.SendFromEmail, this.SendFromName);
EmailMailMessage.Subject = this.SendSubject;
// ensure encoding is correct for Arabic/Japanese sites and body transfer method is correct
EmailMailMessage.BodyEncoding = Encoding.UTF8;
EmailMailMessage.BodyTransferEncoding = TransferEncoding.QuotedPrintable;
SmtpClient client = new SmtpClient();
// this in a try catch and more complex
client.Send(this.EmailMailMessage);
}
</pre>
I have tried playing about with the encoding formats, just adding one alternative view and so on but cannot seem to get it to send out the same email as my old ASP Classic code e.g a multipart email with 2 boundaries, 1 for the text version WE WANT TO USE and one with the HTML version. It always seems to create it's own Plain Text version from the HTML version which I don't want to happen.
Any help or ideas would be much appreciated.
Thanks in advance for any help!
The answer seems to be that there is a bug in the MailMessage class. I have been told to report this as such on the Microsoft .NET forum.
It seems that the issue lies in the use of LinkedResources.
If I remove the code that adds the LinkedResources to the HTML alternative view then the code works fine and I can see both my Plain Text and HTML views in my mail client.
Therefore I have to leave the images as externally linked resources that are loaded into the email when the user presses any "load remote content" button in their email client.
I have created a community portal, in which user creates his/her account. After successfull registration a confirmation mail is send on registered email address.
I am using the following code to send the mail -
private void SendMail(string recvr, string recvrName, string verCode, int NewUserID)
{
try
{
string emailID = ConfigurationManager.AppSettings["WebMasterMail"];
string mailPass = ConfigurationManager.AppSettings["pass"];
string mailer = ConfigurationManager.AppSettings["mailer"];
MailMessage msg = new MailMessage();
MailAddress addrFrom = new MailAddress(emailID, "Panbeli.in.... Bari community portal");
MailAddress addrTo = new MailAddress(recvr, recvrName);
msg.To.Add(addrTo);
msg.From = addrFrom;
msg.Subject = "You have registered sucessfully on PanBeli.in.";
msg.Priority = MailPriority.High;
msg.Body = RegisterMessageBody(recvrName, verCode,NewUserID);
msg.IsBodyHtml = true;
SmtpClient smtp = new SmtpClient(mailer);
smtp.Credentials = new System.Net.NetworkCredential(emailID, mailPass);
smtp.Send(msg);
}
catch (Exception Ex) { }
}
While testing we found that all the confirmation mails are going to SPAM folder instead of Inbox.
Is there anything wrong with the code or is there anything related to security.
Can anybody suggest solution to this problem.
Thanks for sharing your time.
It sounds like your email is getting flagged by SpamAssassin or the like, so you just need to focus on changing your email enough to not get flagged.
Your content doesn't sound like it has any reason to rate high for the Bayesian score, so I don't think thats the problem. It wouldn't hurt to try removing possible trigger words though.
Your message is marked with high priority. Do you need this? This just adds into one of the scoring metrics in a spam filter. Spam is often marked with high priority, so your message will be treated with more scrutiny. On the otherhand, for some filters marking your message with high priority will mean less scrutiny.
IsBodyHTML is marked true, but you're only providing text/html. You minimally need to include an alternate view with text/plain.
message.IsBodyHtml = true;
string html = RegisterMessageBodyHtml(recvrName, verCode,NewUserID);
string plain = RegisterMessageBodyPlaintext(recvrName, verCode, NewUserID);
message.AlternateViews.Add(AlternateView.CreateAlternateViewFromString(html, new ContentType("text/html"));
message.AlternateViews.Add(AlternateView.CreateAlternateViewFromString(plain, new ContentType("text/plain"));
See how Google treats your message. In gmail, open a test message that you've sent, click the downfacing arrow next to the reply button, and select "Show Original". You'll see how Google treated your message. Look for headers like:
Received-SPF: softfail (google.com: domain of transitioning xxx#xxx.org does not designate xx.xx.xx.xx as permitted sender) client-ip=xx.xx.xx.xx;
Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning xxx#xxx.org does not designate xx.xx.xx.xx as permitted sender)
Read up on the default rule set for SpamAssassin as it will probably be a good reference on the rule sets for most filters. If you can identify why your message is getting flagged, you can fix it.
Emails Marked as Spam
This is not a programming issue unfortunately, but I can understand why you might think it is. The code is sending the emails, and they have been sent as you reported. So this is highly unlikely to be a problem with your code, because it's served it's purpose fully!
Getting around it
It all comes down to the recipients mail client (the software they are using to view the emails with), or the services that process the emails at some sort of gateway, or a combination of both of these!
All of these elements have vastly varied algorithms and metrics for determining if an email is probably spam or not. So a one fit all solution is sadly not possible. Some are intelligent, other less so, some brutally discard a huge % of emails, others operate purely on a 'not on white list, you're not getting in' policy, and then there are those that just let everything come in regardless of content/origin.
The ways to go around fixing this are:
To try and get on white lists for major email providers.
Educate your audience to add the senders email address as a trusted contact.
Check your mail server IP isn't blacklisted by some providers. It's possible your IP address was previously used to send spam.
Experiment with the emails content
Your from address is invalid. Try putting in a real email address that points to a valid mailbox. Preferably this email address is on the same domain as the SMTP server you use to send the mail with. If not, read into SPF http://en.wikipedia.org/wiki/Sender_Policy_Framework
This happen to me to and it's solved now,
I just set the BodyEncoding and SubjectEncoding proprieties on the MailMessage object,
and added the DOCTYPE and the html tags to my email header,
var msg = new MailMessage
{
Subject = subject,
Body = body,
BodyEncoding = System.Text.Encoding.UTF8,
SubjectEncoding = System.Text.Encoding.Default,
IsBodyHtml = true
};
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
It's working perfectly now
Add following line in your code while creating MailMessage
msg.BodyEncoding = System.Text.Encoding.GetEncoding("utf-8");
This happens a lot even for the house hold names. I sympathise with you as you only want a plain text email but if your clients really want those emails and you really want your logo in then they could just white list your domain so that all emails get through!
We use a company called mailchimp for sending out subscriber mails and I questioned them on how to avoid spam filters especially in the context of essentially an advert out to a large group it can be very difficult to avoid them, here is their advice and there is lots of it.;
Avoiding the Spam Filters
For anyone having this problem, it looks like Google mark as spam any mails using the default ASP.NET e-mail authentication subject and body. I.e.:
"Please confirm your account by clicking here."
Changing the text allows the e-mail to pass the spam filter
I have a windows forms application that I am adding a request support form to, and would like the user to be able to input the values and hit a button. Once the button is pushed I can either:
Open a new mail message and auto populate the message. (Not sure how to do this)
Submit the request via a http form on my website. (I know how to do this)
Send an email directly from the code of the application. (I know how to do this)
What I want to know is what would be the best method to use? I think option 1 is the most transparent, and the user will see exactly what is being sent, but I am not sure how to ensure it works no matter what email client they use.
I see there being potential issues with option two, specifically a firewall possibly stopping the submission. But option 2 would allow me to supply them with a ticket number right then and there for their request.
Thanks for the help.
For Option 1, as suggested, use the mailto handler.
Format your string like so: string.Format("mailto:support#example.com?subject={0}&body={1}", subject, body). Don't forget to UrlEncode the subject and body values.
Then use System.Diagnostics.Process.Start() with your string.
This will launch the registered mail handler (Outlook, Windows Live Mail, Thunderbird, etc) on the system.
For option 1 : If the message body is short, then invoking the mailto handler from inside your code no longer requires that they be using outlook. It's kinda a cheap hack, but it's completely cross-platform for local mail clients. (If they're using something like gmail, you're still SOL, though)
Option 2) is the best to avoid enterprise firewall issues because the HTTP port may not be blocked.
Option 2) is the best for simple configuration. The only config key you will have is the service/page url. Then your SMTP configuration will stay on your webserver.
Now you will have to choose between using a webpage (if one already exists) or a webservice (which is best fitted for your feature).
For option (1) be prepared to deal with Outlook version problems. But this is not hard (again if we are talking about Outlook, last version)
//using Microsoft.Office.Interop.Outlook;
private void OutlookMail(string Subject, string Body)
{
ApplicationClass app = new ApplicationClass();
NameSpaceClass ns = (NameSpaceClass)app.GetNamespace("mapi");
ns.Logon("", "", true, true);
MailItem mi =
(MailItem)app.CreateItem(OlItemType.olMailItem);
mi.Subject = Subject;
int EOFPos = Body.IndexOf(char.Parse("\0"));
if (EOFPos != -1)
{
log.Error("EOF found in Mail body");
ErrorDialog ed = new ErrorDialog(TietoEnator.Common.ErrorDialog.ErrorDialog.Style.OK, "Export Error", "File could not be exported correctly, please inform responsible person", "", "EOF char detected in the body of email message.");
ed.ShowDialog();
Body=Body.Replace("\0", "");
}
mi.HTMLBody = "<html><head><META content='text/html; charset=CP1257' http-equiv=Content-Type></head><body><table>"+Body+"</table></body></html>";
mi.BodyFormat = OlBodyFormat.olFormatHTML;//.olFormatPlain;
mi.Display(0); // show it non - modally
ns.Logoff();
}
BTW for automatic support requests I plan to use in my current project "Microsoft Enterprise Logging Support Block" email sending functionality.
I have written an program in C# which sends out emails. Now I have a requirement to sign outbound emails using Dominkeys/DKIM, but I'm not sure how to do it.
I have set up all keys, but I don't know how to get those and how to include them in the email header.
There is a fundamental problem with trying to do DKIM signatures with System.Net.Mail.MailMessage and System.Net.Mail.SmtpClient which is that in order to sign the message, you need to poke the internals of SmtpClient in order to hash the message body as one of the steps in generating the DKIM-Signature header. The problem comes in when you have alternative views or attachments because SmtpClient will generate new multipart boundaries each time it writes out the message which breaks the body hash and thus the DKIM-Signature validity.
To work around this, you can use the MimeKit and MailKit open source libraries for .NET as an alternative framework to using System.Net.Mail.
To add a DKIM signature to a message in MimeKit, you would do something like this:
MimeMessage message = MimeMessage.CreateFromMailMessage(mailMessage);
HeaderId[] headersToSign = new HeaderId[] { HeaderId.From, HeaderId.Subject, HeaderId.Date };
string domain = "example.net";
string selector = "brisbane";
DkimSigner signer = new DkimSigner ("C:\my-dkim-key.pem", domain, selector)
{
SignatureAlgorithm = DkimSignatureAlgorithm.RsaSha1,
AgentOrUserIdentifier = "#eng.example.com",
QueryMethod = "dns/txt",
};
// Prepare the message body to be sent over a 7bit transport (such as
// older versions of SMTP). This is VERY important because the message
// cannot be modified once we DKIM-sign our message!
//
// Note: If the SMTP server you will be sending the message over
// supports the 8BITMIME extension, then you can use
// `EncodingConstraint.EightBit` instead.
message.Prepare (EncodingConstraint.SevenBit);
message.Sign (signer, headersToSign,
DkimCanonicalizationAlgorithm.Relaxed,
DkimCanonicalizationAlgorithm.Simple);
To send the message using MailKit, you would do something like this:
using (var client = new MailKit.Net.Smtp.SmtpClient ()) {
client.Connect ("smtp.gmail.com", 465, true);
client.Authenticate ("username", "password");
client.Send (message);
client.Disconnect (true);
}
Hope that helps.
see https://github.com/dmcgiv/DKIM.Net it's a DomainKeys Identified Mail (DKIM) implementation for .Net written in C# - it enables you to sign MailMessage objects.
Use
http://www.mimekit.org
Not only does it allow to use DKIM for signing, also you can include S/MIME certificates, PGP certificates and more.
Also, its a very mature lib - the only one i've found that handles foreign languages (apart from english) correctly, since its completely and thoroughly coded with unicode in mind.
Its free and opensource.
This solved it for me when using Mailenable as SMTP relay server.
http://www.mailenable.com/kb/content/article.asp?ID=ME020700
When creating the DKIM TXT record on the domain name don't forget to use the active selector as prefix => yourselector._domainkey.yourdomainname.be
If you are looking to DKIM-sign the body of the MailMessage then DKIM.NET is great. If you are looking to have alternative views in your message then I wasnt able to find a solution and wrote my own (open-source with the usual disclaimers) that can be found at https://github.com/yannispsarras/DKIM-AlternativeViews
I understand this is a pretty old thread but I thought it may help someone.
i didnt find much help on this issue, but my problem got solve by configuring smtp server.
i cant post those steps as i am using 3rd party smtp server and every server has their own configuration. after proper configuration my smtp automatically adds DM/DKIM signature.