I've been tasked with creating some sort of service that will take any e-mail sent to an e-mail address and handle the contents of the e-mail (including binary attachments.)
I've got full access to the server (Windows Server 2008) that will run this service, and have decided to code the solution using the .NET framework (3.5).
Now I'm thinking about the different ways I can do this. Since I'm not very experienced in handling e-mails programmatically, the first solution that came into my head was to create an e-mail client that will periodically poll an existing e-mail server for incoming e-mail (using the POP3 protocol) and process them. But there are other ways to do it.
One could be to use IMAP to stay connected to the mail server and fetch e-mails as soon as they arrive (more responsive, but I believe the IMAP protocol is harder to implement.) The follow-up question here is: where can I find reliable e-mail libraries that support the POP3 or the IMAP protocol?
Another could be to somehow configure the e-mail server to directly pipe the e-mails sent to a specific address to my binary code (I've seen this done on Linux servers.) I have no idea how to go about this, though.
The last I can think of would be to create a dummy e-mail server on its own address that handles the e-mail directly as it arrives, but to me this seems like a bad idea.
Does anyone have experience in this area? I would imagine that having to write e-mail handlers for ticket support systems isn't that uncommon, all I need in addition to that is to handle the attachments.
I'd be grateful for any hints and tips.
As with alot of things - it depends. Ask yourself the following questions:
What are your latency requirements--do you need to process incoming messages as quickly as possible, or can processing be batched? If it can be batched, then how often would you have to process the "inbox"?
What are your throughput requirements? How many messages are we talking about per minute here? How big are the messages? This would affect the decision you make about polling interval if using a batch scenario;
What sort of e-mail system are you integrating with? If it's Exchange, what programmatic interfaces are available to access a mailbox? Until the most recent version of Exchange, interestingly enough, there were issues with accessing a mailbox on an Exchange server (The client-side CDO COM components needed to be used which is not ideal---and there were security limitations).
By far the simplest approach is to poll a mailbox using POP3. However, if you need to respond immediately to an incoming message, then this isn't going to cut it.
As far as possible avoid writing your own SMTP service--it's been done a thousand times before and you're just creating unnecessary work for yourself and exposing yourself to security threats. If you absolutely have to respond immediately to messages, then rather set up an instance of Sendmail or Postfix to spawn a process that you have written.
If you're going to go for the POP3 solution (it looks like you are), then have a read of related questions "Free POP3 .NET library?" and "Reading Email using POP3 in C#".
I've used webdav in the past with c# to access an exchange server periodically and process emails.
This has worked quite well, and I'd probably use that method again if I need to do it.
Some of the .net components from http://www.quiksoft.com/ might help with your requirement.
The app polls a POP3 mail server every x minutes(s) and works it's way through the messages in the queue, and deletes them when it's processed each msg.
The QuikSoft tools also provide ways to parse the emails to get the content from each msg.
Receiving the email is not the hardest part, parsing, extracting attachments is.
If any one is interested in commercial product take a look at Mail.dll.
It supports IDLE command you have mentioned for instant notifications.
Mail.dll includes POP3, IMAP clients and powerful MIME parser:
using(Imap imap = new Imap())
{
imap.Connect("imap.server.com");
imap.Login("user", "password");
imap.SelectInbox();
List<long> uidList = imap.SearchFlag(Flag.Unseen);
foreach (long uid in uidList)
{
IMail mail = new MailBuilder()
.CreateFromEml(imap.GetMessageByUID(uid));
Console.WriteLine(mail.Subject);
}
imap.Close(true);
}
Please note that this is commercial product that I've created.
You can download it at http://www.lesnikowski.com/mail
Related
We have to set up a notification system which needs to reliably deliver notification emails to clients.
In the past we have used .NET's System.Net.Mail.SmtpClient libraries to quickly hook up and send various low-priority emails. Reliable and effective delivery wasn't critical.
Now we need to be able to delivery emails to clients - a different story.
Is it worth using some third-party service (like SendGrid) or is the regular SmtpClient just fine?
We don't need any analytic, marketing or subscription features. Our volume requirements are not huge either - perhaps 10k per day. Only email sending capabilities are required.
Is it worth using some third-party service (like SendGrid) or is the regular SmtpClient just
fine?
Absolutely wrong question as you compare a sending API with a full-fledged email server.
You should have your local email sending relay either local on the machine (smtp service) or in your network and SmtpClient should go to that one. This then relay the emails - either to the end users or to a distribution service (sendmail).
I would NEVER use a setup where the web app has to directly send via a remote third party. This is bound for all kinds of problems. As such, the question whether it is something like SendGrid or SmtpClient never would even be considered. It would never show up - it would be BOTH. Plus a local relay. There are some nice third party email servers that are free as long as you have a LOW list of LOCAL Mailboxes - which means that they are perfect free email relays.
Companies like SendGrid (for whom I work) focus on deliverability and making integration really simple for developers.
You can certainly implement your own solution with success, provided you have the time. We have a free Deliverability guides that helps you do that, here are a couple: http://go.sendgrid.com/Deliverability-Guide-V2.html and here: http://sendgrid.com/blog/10-tips-to-keep-email-out-of-the-spam-folder
We regularly post tips for deliverability on our blog at http://sendgrid.com/blog
I am developing a site for which I would like to protect buyers by anonymizing their email addresses.Similar to craigslist's system, when a seller needs to contact a buyer they should be able to send an email to an anonymized address such as 1425415125#mysite.com which will then be routed to the user's email address.
My plan right now is to:
Set up a bucket (catch-all) inbox
Generate a random key for each buyer which will be the user specific ('1425415125' above) section of the email address
Monitor the bucket inbox and parse out this user specific section. Once I know the user, the email can be forwarded to the correct address
My questions are as follows:
Can you see any issues with the above solution
Are there any open source solutions to the existing problem
Are there any gotchas that one should be aware of when developing such a system?
Thanks in advance
JP
I did something related, though not quite the same. I setup a catch all inbox on my existing pop3 server (you probably have one already I'm guessing). I then used OpenPop.NET to read all new messages on a timer (say every 30 seconds). In my case I stopped at just processing the messagse but it's easy enough to generate a new message to the appropriate address and copy the body over, then send the new message out on your SMTP server.
One problem I see with your setup, and maybe it's just a misunderstanding on my part, is that while you are protecting the users original email address they will continue to be reachable at 1425415125#mysite.com basically forever. If I understand the way craigslist works, each posting has a different email address, and once the posting has been deleted/removed (or shortly after) the email address stops working. This makes it so that people can't just keep bugging you on that email address. The solution to this issue is easy, just make the email address coorespond to a post id or some other id rather then the users id in the database. The lookup will be just as quick but they will have a new email address each time.
You may wish to look at mail "piping" - the ability for someone to send an email to a mail server, which then gets thrown immediately to an executable, which then forwards your mail onto the recipient (by pulling the real email address from the database based on the incoming address from the piped message).
My personal recommendation would be to check out HMailServer, which has a COM API (the admin side is written in PHP, hence the requirement for legacy interop), is free and open-source, and is very well-documented. It doesn't have mail piping built-in, but is easily extensible given the API and support for scripts which run on server-side message events
HTH,
Benjamin
I think this solution will make sense and is in use in a lot of cases. The hardest part is actually receiving the messages. You can actually handle all of this within your web app if you need to. I wrote a blog post highlighting a couple of ways to receive email in your web app. It applies mainly to Rails but the concepts should be transferable.
The way you are lookimg to do it is the way I created a similar service. I would not recommend you writing your own smtp server. Use an existing mailserver and just use polling or some event based api.
The benefits of using a 3rd party mailserver is you can use existing backup and management tools on it.
Edit: I just noticed this has beed answered here with a better explanation. Pipe incoming email to a script on Windows IIS SMTP?
I do not see any problem with your setup, infact that is correct way to do because if your scheduled application fails, the emails will still be in the catch-all email box. Only once the email has been successfully delivered to somebody, the email should be deleted. You will be able to monitor and log the activity of your own application to monitor progress and failures.
I do not recommend Piping because, if for any reason piping goes successfully but your exe crashes, you will loose the email. Tracking will be difficult. Scheduling the jobs will not be possible.
If your application is independent of mail server, it is easy to manage it and replace your mail server whenever possible. It is easy to extend.
In this you will have to use some pop reader library, and schedule your application to run frequently.
In addition to email, you may consider a pull rather than push delivery mechanism, e.g: a message center web frontend or RSS feed. I say this because deliverability problems to various ISPs can be very difficult to troubleshoot and in my experience your users will never believe it's their ISP.
I am building a web site, and the client wants a newsletter "system" on it.
How do I send this kinds of mass (>1000) emails?
I read somewhere that using sendasync method of the smtpclient does the trick.
But it constantly gives me an "Email faliure" exception. And, I don't know what to do with that right there...
So, basically my question is, is it ok to send the emails using the SEND method of the smtpclient, but each mail in it's own thread.
for eg.
NewsletterEmail newsletterEmail = new NewsletterEmail(emailAdress[i], mailSubject, mailBody);
Thread t = new Thread(new ThreadStart(newsletterEmail.MakeAndSendEmail));
t.IsBackground = true;
t.Start();
i think , you should rethink about your startegey for sending bulk emails
Creating > 1000 threads is not a good idea , it may even crash your server or it may make your server respond very slow.
Tell your client about Constant Contact. They are going to handle this much better than you ever could. It's also cheaper than your time.
In the event that fails you have a couple options.
If they already have an email server, leverage that to do the email broadcasting. In other words, relay the mail through that server.
If you can't do that, go download a free email server. I've been using hMailserver. Set it up and relay through it.
If you can't do that, write your own SMTP processing engine. Don't attempt to send the emails directly from ASP.Net. Queue them up in a database and write a windows service to handle the mail broadcasting.
Sending emails can sometimes take several seconds per email. This could completely hose your website while it's trying to handle sending 1000 emails.
A number of mail servers are configured with grey listing, meaning that they require you to send the same email twice in order to prove you aren't a spammer.
Next, getting the DNS appropriately set up can be a PITA. Which is why I suggest constant contact. I have one client that took nearly 5 years to finally get their DNS configured; and yes, I gave them explicit instructions once a year on what to do. Reverse DNS is critical.
Another thing is that some recipient servers have a limit on the number of threads they will accept from you at once. Most mail servers are built to take this into consideration. If you cross that boundary, then the recipient servers will consider you a spammer and take appropriate action.
Another problem area is in sending to a bad address, over and over again. AOL and others will consider you a spammer just for this one thing.
Point is, you really don't want to write this yourself.
Your best bet would be to have a separate process send the emails. Either have it run on a schedule to check for emails that need to be sent (maybe store the emails in a table?), or, if you don't like the scheduled process idea, then you can have a console application that is started by your website.
Something else to keep in mind is that if you are sending too many emails in a short period of time, it becomes very easy to get black-listed and then none of the emails from your domain will make it to any servers that have you black-listed.
I've taken two approaches:
1) Lazy, sloppy approach of configuring the asp.net process timeout long enough to complete via Send
2) Create a console app that is spawned by the web app.
I built a similar system a year or two ago. There's so many things that can go wrong when you send an email programmatically. For this reason, do yourself a favor and seperate the messages from the process of sending them. This way, you can "teach" your system that "badEmail#goodDomian.com" should be ignored or other similar situations.
You can store the message, subject, or whatever level of seperation of data you desire in the database along with a flag for meta-data like "SentOn", "FailedOn", etc. I sent my message one at a time to allow for individual errors to be stored and/or handled. I used SmtpMail.Send(), but whatever method you choose should work as long as you built something smart and recoverable.
Have a look at the MailChimp API: http://www.mailchimp.com/api/gettingstarted/
ASP.NET Webforms application.
Problem: How to implement emailling elegantly?
Many parts of the application demand it. This will include HTML emails, solutions how to handle bouncebacks etc..
I have the option to use my own SMTP server (app is hosted on a VPS), or to use the hosting providers.
I'd like to start logging here too (log4net probably)
Any suggestions for libraries to use / patterns to implement?
EDIT: http://martinnormark.com/2010/03/13/generate-html-e-mail-body-in-c-using-templates
I like having a debug catch asp.net net.mail - route all emails to a different email address in debug mode
For testing with a faked out SMTP server use ndumbster. Phil Haack has a blog post on usage - http://haacked.com/archive/2006/05/30/ATestingMailServerForUnitTestingEmailFunctionality.aspx
As you pointed out email templates are fantastic. Consider creating a template for HTML and plain text. Make sure your HTML email templates use basic HTML as a number of email clients out there are not up to modern day browser standards (eg. Outlook which uses the Word HTML rendering engine).
Log4Net is a good point to start at with logging. You can also use System.Diagnostics for simplistic tracing and debugging which can be written easily out to the event log or a file. I always prefer to have a wrapper for all logging so that logging frameworks can easily be swapped out if you find that you want to swap them out later because of a must have feature. It's also good from the point of testability as you can mock it out easily.
Really it doesn't matter which SMTP server you use as long as you don't get black listed. Make sure you check the SMTP servers IP against a DNSBL so you know if your SMTP host has a bad reputation. I highly recommend checking it using Barracuda Central's IP reputation - http://www.barracudacentral.org/lookups. Also make sure you're SMTP server does support resending when you're recipients use grey listing.
For bounce backs you can setup a POP account for it to send back to, it could be as simple as reading the emails and finding which email account the rejection came from and the subject of the previous email (which should be unique) so that you can send again later or after several bounce backs remove them from the list. To implement reading POP take a look at this thread - Reading Email using Pop3 in C#
The best pattern you can implement to save yourself loads of trouble down the road is not to send email directly from your web application. Instead, write the email (or the info you need to generate the email) to a database and have a separate process do the mailing.
Consider what happens when your smtp server is down and your app tries to send. If you have a separate process sending email you can send the email later when its back up.
Also you gain the ability to rate limit your outgoing email. If you end up with the Next Big Thing® on your hands you'll be glad you now have the ability to prioritize your outgoing mail or send mailing lists in batches instead of crushing your smtp server at the high point of your site's traffic.
If you are working with bouncebacks just have this process handle that as well. Now you have the ability to log a returned email address to a blacklist and check against the same list for every outgoing email. No way you want to have to put all that in your web app.
Regardless of what else you come up with please consider just writing the email to be sent to a database and letting your app go about its business. You can still get the message going out in near real time but you can get a real good separation of concerns with little effort.
As for incoming messages, I have had great success with the hMailServer which is a free e-mail server for Microsoft Windows. It supports the common e-mail protocols (IMAP, SMTP and POP3) and can easily be integrated with many existing web mail systems. It has flexible score-based spam protection and can attach to your virus scanner to scan all incoming and outgoing email. Definitely worth looking into.
For outgoing emails, I like the patterns I've expressed in this article: .NET MailMessage, LinkedResources, AlternateViews and Exceptions
Can anyone recommend a simple and reliable method of sending email notifications and possibly log files attachments from a C# program without requiring the installer or the user to configure the program by specifying server details and email addresses etc.
(Mainly because they won't know the details, but also because they could change)
The program will normally be run as a service of a Windows Server, but can be run on a client.
I tried connecting to our own mail server and sending a email to myself, but some ISP's are blocking Port 25 on all servers but their own, so that method isn't working reliably.
Tried sending email through gmail but that was less successful as the port they used was blocked by firewalls. Ditto webservices connecting on weird ports.
Trying to use the local smptservice but did not work either.
It would be nice, but not essential if it was not dependant on my own Internet connection/Servers. (Don't mind them being delayed, but prefer them not to get lost).
Are there any webservices on http/https that allow you to do this sort of thing?
TIA
try using cdosys
http://support.microsoft.com/kb/310212
http://www.eggheadcafe.com/articles/20030316.asp
May have discovered the solution.
Was catching up on my blog reading over the weekend and came across a recent entry on Coding Horror and the very first comment mentions PostMarkApp which seems to do everything I need (and almost everything I want, apart from attachments which they are considering).