I used smtpclient to send emails, but finally i found that some of the emails can not be reached.
for example:
receiver: aaa#123.com
sometimes, the emails we send to it , and it will receive successfully, but sometimes will not.
at the beginning, I thought it might because that smtp didn't send it successfully, then I use client.sendAsynce, and then add the event handler to handle the SendCompleted event, and i found every emails are sent out successfully, and then we check the smtp server, it really received all the emails and sent out successfully.
So the problem is why sometimes the emails will not be reached successfully, and sometimes will be OK?
You're forgetting one piece of the puzzle - the client email server. Perhaps the emails are being rejected or flagged as spam?
Related
I bumped on this error while trying to help a developer resolve a bug.
He was having issues with mails that were supposedly send but never arrived. Checking the code and the msg we came to the conclussion that the text that was caousing the issue was "0880". So i made a test page with a button and the following code on it:
SmtpClient cl = new SmtpClient("exchangeserver");
cl.Send("mail#from.com",
"mail#to.com",
"Test",
"0880");
Much to my surprise even thou the Send function executes and doesnt throw an exception the mail never arrives. If i replace the text in the body with other string, say "this is a test mail" the mail arrives fine.
I tried using MailMessage class with the Send() with and without HTML, i even tried using gmail smtp server instead of my company exchange server, but the result its always the same the mail with the 0880 never arrives, all the other strings ive tried do.
Any ideas?
Thanks
What is the best way to be notified instant when mails or changes happens to the INBOX of my mailbox using MailKit??
I have been playing around with following events:
ImapClient.Inbox.CountChanged; This seems to work best when using Exchange servers, since they don't react at all on the MessageArrived event. Pff..
ImapClient.Inbox.MessagesArrived; This seems to work quiet well with open source mail servers, like SquirrelMail, but doesn't work at all with Exchange.
I want to be notified when new mails arrive to the mailbox, if any mails are moved/deleted, and if there any mails moved to this imap folder. Which approach should I take to get an event asap when something happens to my INBOX?? I want the best of both worlds.
And what is the ImapClient.Inbox.Subscribe(); used for??
The Subscribe and Unsubscribe methods just flag a folder (aka mailbox) as subscribed or unsubscribed - generally this is only used by mail clients to decide whether or not the user wants to see the folder in the default folder list.
The CountChanged event is emitted anytime MailKit gets an untagged "* # EXISTS" line from the IMAP server, typically as part of a response to a command that was just sent.
The MessagesArrived event is emitted immediately following the CountChanged event IF AND ONLY IF the new message count is larger than the old message count. Unfortunately, this is a badly designed/named event because it can be very misleading. Since the logic that determines whether or not to emit the event only has limited context (the old message count and the new message count), it can't accurately decide whether or not to emit this event.
Take the following situation for example:
When you open a folder, let's say that the message count is 10.
Now you expunge a handful of messages (5?) out of the folder... BUT, while the messages are being expunged, you get 2 new messages.
When the expunge command completes, the IMAP server replies back with "* 7 EXISTS"
Since 7 (the new message count) is less than 10 (the old message count), the MessagesArrived event will not be emitted.
I want to be notified when new mails arrive to the mailbox, if any mails are moved/deleted, and if there any mails moved to this imap folder.
If you want to know when new messages arrive, you need to listen to the CountChanged event and do your own book keeping to figure out if new messages arrived or if messages were moved/deleted out of the folder.
There's no way to distinguish between messages being moved into the folder vs new messages being delivered to the folder (unless you are doing the moving).
Which approach should I take to get an event asap when something happens to my INBOX??
If your server supports the IDLE extension, you'll probably want to look into using the ImapClient.Idle() (or IdleAsync()) method since the CountChanged event will only be emitted when it receives a "* # EXISTS" response from the server, and an IMAP server will only send that response as part of a response to a command from the client or if the client is in the IDLE mode.
If your server does not support the IDLE extension, you will need to "ping" the IMAP server using the ImapClient.NoOp() method (which is a dummy command that doesn't do anything) periodically in order to check if any new messages have arrived since the last command you sent.
There's an ImapIdle sample in MailKit's GitHub repository to see how to use it.
I have an application which uses SmtpClient to send an email. I am trying to send an email to multiple recipients. I have two recipients in my to list e.g "aman#gmail.com,abc#xyz.com". and I am trying to send the email to this list but my application is throwing the exception as below:
Client does not have permission to submit mail to this server. The server response was: 4.7.1 (abc#xyz.com): Relay access denied.
because of this aman#gmail.com is also not able to receive the email.
I need to implement the functionality that even there is an invalid address like abc#xyz.com in the ToList, an email should be sent successfully to aman#gmail.com.
Can anybody please help me in this?
Does this error message come from your own email server, or from that of xyz.com? I'm guessing it's your own server, and that you either need to aunthenticate before sending, or use your own email address for sending (but the latter is kind of a long shot -- "we do not relay" means a server which is neither the sender's or the recipient's refuses to act as a middleman). It is also possible that the mail exchanger for xyz.com is misconfigured (either the MX record in DNS points to the wrong server, or the admin failed to configure it to accept this responsibility - technically basically the same thing) or that your client somehow ends up connecting to the wrong place.
(Not a proper answer but this got too long to fit in a comment.)
The SmtpClient send method returns void. Is there any way to get the server response? Do I just assume it was successful unless it throws an exception?
The class I'm referring to... http://msdn.microsoft.com/en-us/library/system.net.mail.smtpclient.aspx
To answer your second point, yes, all you can do is assume it's successful - meaning it got the message to the server and the server accepted it, unless you get an exception.
You probably already know the rest of this, but just in case...
From there, the email could get lost and not delivered any number of ways. Your server may accept it and decide not to send it, or accept it and lose power before crashing. It may get blocked by a spam filter along the way, etc.
You can think of an email as being similar to a regular piece of mail in that it passes through several hands between the sender and the recipient. From your code, you can only confirm that it got to the SMTP server you're using to send, which is similar to handing it to a teller at the post office. You don't know (or need to know) how the message is routed from there. it could be by air, ground, or carrier pigeon. You're out of the equation - you don't need to know how it gets sent, just that you trust that they know how to send it. (The same can be said for an email.)
If you need to confirm that the recipient opened it, there are ways of embedding an image in an HTML message on your server and tracking in your logs when that image is accessed, etc. (Google email tracking and email open tracking)
On the other hand...
If the server rejects it, then you do get a server response in a manner of speaking - there should be an error code and a description in the error, which you can use to troubleshoot why it didn't make it, or use error handling to try another route, etc.
You can utilize SendCompleted Event to check that your smtpclient works fine like this:
http://msdn.microsoft.com/en-us/library/system.net.mail.smtpclient.sendcompleted.aspx
But you cannot get confirmation that your message reached recipient because it may stuck in any server/filter in message chain.
You assume that it was successful unless it throws... although success in this case only means that it was accepted by the mail server, anything else is then up to the server...
IF you want a little bit of control you can use SendAsync and hook the SendCompleted event...
I was wondering if anyone could help me out (not with code, although that would be appreciated), with the logic behind checking and retrieving messages from a POP3 mail server.
I.e.
Establish connection
Validate credentials
Enumerate message list
Check each message to see if it's "new"
Download "new" message(s).
Would this be the correct way about doing this?
Thank you
The best way of looking at something like this is to have a look what something else does. Run Wireshark or some other packet capture software, and use an e-mail client to check. Anyway, the basics of a POP3 session are as follows:
USER username
PASS password
LIST <-- Shows the size of each waiting message
UIDL <-- Shows a unique ID for each waiting message
RETR 1 <-- Retrieves message with index 1
DELE 1 <-- Deletes the message you just retrieved
QUIT
The first char of all of the responses except RETR will be a + (success) or a - (failure).
If you are deleting messages off the server after retrieving them, you don't need to bother with UIDL. If you are leaving them, you can use UIDL to get a unique ID for each message which you store locally to show you have retrieved that message before.
For more details, see the RFC. Wikipedia also lists a more in depth example, showing the server response.
These should be useful:
POP3 Email Client (.NET 2.0)
POP3 Client as a C# Class
Retrieve Mail From a POP3 Server Using C#
POP3 Sequence Diagram
POP3 Reference