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MailBee.NET SMTP

AfterLogic Forum : MailBee.NET SMTP

Topic: Sending multiple emails via threads

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Neil_Knight
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Posted: 20 January 2012 at 4:47am \| IP Logged

I am creating an application that is sending multiple emails via threads. I'm using the SMTP class in order to create my emails and send. When I run the application with 1 thread, the system works fine. If I increase the number of threads, then I get input in the log files from other threads, even though they aren't logging to that file. This is breaking the whole system. Any idea as to why a thread is interrupting another thread? Is the SMTP class thread-safe?

Igor
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Posted: 20 January 2012 at 5:13am \| IP Logged

Is my understanding correct that you are using single SMTP object instance for all the threads? If yes, they will all use a single log file, and you'll need to make sure SyncRoot property is set correctly. It is still possible to have different log file for different thread, the example is available here. Alternately, you can simply use separate SMTP object instance per thread, that should not affect overall performance.

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Igor, AfterLogic Support

Neil_Knight
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Posted: 20 January 2012 at 5:40am \| IP Logged

Hi Igor,
I am using seperate Threads in order to instantiate an SMTP object and then connect, configure and send the email.

Neil_Knight
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Posted: 20 January 2012 at 6:30am \| IP Logged

Here is an example from the log file:

[14:19:28.68] [INFO] Socket connected to IP address 68.232.135.98 on port 25.
[14:19:30.16] [INFO] Connected to mail service at host "mx1.dhl.iphmx.com" on port 25 and ready.
[14:19:30.16] [INFO] Will send Hello command (HELO or EHLO).
[14:19:30.31] [INFO] SMTP Hello completed.
[14:19:30.43] [INFO] Will send mail message to SMTP server "mx1.dhl.iphmx.com".
[14:19:30.45] [INFO] Will submit sender and recipients.
[14:19:30.93] [INFO] Sender and recipients accepted by SMTP server. Will send message data now.
[14:19:32.15] [INFO] Message successfully submitted to SMTP server.
[14:19:32.62] [INFO] Will disconnect from host "mx1.dhl.iphmx.com".
[14:19:32.62] [INFO] Disconnected from host "mx1.dhl.iphmx.com".
[14:19:37.88] [INFO] Will send Hello command (HELO or EHLO).

The last line shouldn't be there.

Alex
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Posted: 21 January 2012 at 12:23am \| IP Logged

To confirm, you're saying that you have multiple instances of Smtp class, each instance running in its own thread, and has its own log file path assigned. Somehow, the log data for Smtp instance #1 appear in the log file for Smtp instance #2.

If you set LogFormatOptions.AddContextInfo flag in Logger.Format property, what do you get?

Regards,
Alex

Neil_Knight
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Posted: 21 January 2012 at 1:13am \| IP Logged

Hi,
I think it might be easier to let you know what I'm trying to do and then you can (kindly) offer the best way of using your component?

I have lots of email addresses in a database, randomly ordered. I select 10 records where they have the same email domain. I then create a new thread and connect to the domain, configure the email with the recipients information and then send it and repeat until I've got no records left. All output goes to a GUID named log file making it unique to the instance of the Smtp object.

This process works when 1 thread is running. When I have multiple threads, it's as if the process messes up some what. It's like it doesn't follow the same pattern that is working for 1 thread.

I'd like to know how I can capture any error that is thrown when the Smtp object is connected and sending/receiving data. Is there an Event Handler that I can hook into? Currently I'm using the MailBee....Exception, but that doesn't seem to work all of the time. If there is an Event Handler for any SMTP error codes, that would make my application logic a lot cleaner too :o)

Thanks

Alex
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Posted: 21 January 2012 at 2:10am \| IP Logged

Quote:

I then create a new thread and connect to the domain

You're NOT using SMTP relay server, correct? Why so, is it for a purpose? Also, when you mention "connect to the domain", do you mean "connect to MX of that domain"? And what if the domain has multiple MXes, some of them are dead?

Quote:

I'd like to know how I can capture any error that is thrown when the Smtp object is connected and sending/receiving data

Smtp class has a number of events including Smtp.ErrorOccurred, Smtp.MessageSent and Smtp.MessageNotSent. They, in turn, have a number of properties like the description of the error, the list of accepted or failed recipients, etc.

Smtp.MessageNotSent event makes sense only when you send multiple messages with a single command (like Smtp.SendJobs). Failure to send a single email (Smtp.Send) throws an exception rather than firing an event.

ErrorOccurred event fires whenever any problem occurred, even if this problem was not critical (warning). You can find more detailed explanations in the docs.

Regards,
Alex

Alex
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Posted: 21 January 2012 at 2:16am \| IP Logged

BTW, error codes and error messages are there too. ErrorOccurred event provides the exception which originated it, through Reason property. And it, like any other MailBeeException, has ErrorCode property which contains that code.

Note that the exception in ErrorOccurred event is just an object, it's not necessarily thrown to the application. Only if IsFinalError is true, MailBee throws the same exception to the application once ErrorOccurred event handler completes.

Regards,
Alex

Neil_Knight
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Posted: 21 January 2012 at 10:55am \| IP Logged

Hi Alex,
I select the records from the database and then create a new thread to talk the the MX server of say Hotmail.com. I am not using a Relay server as I need to do some additional data tracking with regards to the SMTP chat between our servers and the email MX servers.

If I am looping through a data set, and I've configured the ErrorOccurred event, will this break out of the loop? Or does that depend on how I configure a try/catch block around the loop?

If an error does occur, does the code carry on from where it left off?

Neil_Knight
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Posted: 21 January 2012 at 10:57am \| IP Logged

I guess that I can use the ErrorOccurred event in order to reduce some of my code from trying to catch individual exceptions after reading your post. Can I cast the object in the ErrorOccurred event to an Smtp type in order to retrieve more details from the Smtp object? I know that I'll have ErrorCodes and Reason in the EventArgs object.

Alex
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Posted: 21 January 2012 at 12:46pm \| IP Logged

ErrorOccurred event does not control whether to continue execution or not. It depends on your try/catch block. When an exception occurs (I'm talking about "real" exceptions which are propagated to your application, i.e. those which have IsFinalError=true in ErrorOccurred parameters), your application should catch it, analyze it and decide what to do next. MailBee provides very extensive set of exceptions so you can do different things for different exceptions. Also, the state of Smtp object after exception varies upon exception type.

For instance, if the exception implements IMailBeeSocketMustCloseException interface, this means MailBee had to close the connection as this exception is not recoverable. Some exceptions like those which implement IMailBeeNegativeSmtpResponseException interface do not close the connection and you can proceed (for instance, provide other login credentials if the previous attempt failed).

And yes, you can query Smtp object properties and status methods (like GetMaxMessageSize) in ErrorOccurred event. However, it's only allowed if the Smtp instance has only 1 thread. But because you have only 1 thread per instance, you can use this and there is no limitation for your case. More info can be found in Smtp.IsSmtpContext docs.

Regards,
Alex

Neil_Knight
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Posted: 23 January 2012 at 1:15am \| IP Logged

Hi Alex,
Thanks for your help. I'll run a new trial app to see if I can get this configured correctly.

Does the QuickSend method open a connection, send the mail message and then disconnect? Or could I open a connection via the Smtp object, use the QuickSend method and then call a Disconnect?

Igor
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Posted: 23 January 2012 at 2:19am \| IP Logged

That's right, QuickSend methods performs connect and disconnect. If you're doing those operations in your code explicitly, you'll need to use Send method rather than QuickSend.

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Igor, AfterLogic Support

Neil_Knight
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Posted: 23 January 2012 at 2:36am \| IP Logged

Thanks for clearing that up.

Neil_Knight
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Posted: 23 January 2012 at 6:28am \| IP Logged

Ok, so I wrote a new smaller application that I thought I'd simplify the process a bit. Basically I want to do:

Smtp mailer = new Smtp();

mailer.DnsServers.AutoDetect();

// Check the Domain of the recipient and configure an Smtp Server accordingly

mailer.Connect();
mailer.Hello();

// Loop through my records
mailer.Send();

mailer.Disconnect();

However, I can't find anything that will retrieve the MX details of the recipient email address. Any pointers?

Neil_Knight
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Posted: 23 January 2012 at 6:38am \| IP Logged

Effectively, I want to create a "session" with the MX domain server and send multiple emails to different accounts within that domain. Is this possible?

Neil_Knight
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Posted: 23 January 2012 at 6:46am \| IP Logged

Actually, I think that I have found my answer. I need to use Smtp.GetMXHosts().

Neil_Knight
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Posted: 24 January 2012 at 1:50am \| IP Logged

Just a quick thanks to Alex and Igor for your support. I've included the little code snippet should anyone else need to do something similar:

string recipientEmail = "someemail@gmail.com";

using (Smtp mailer = new Smtp())
{
    mailer.DnsServers.AutoDetect();

    string[] mxHosts = mailer.GetMXHosts(recipientEmail.Substring(recipientEmail.IndexOf('@') + 1));

    foreach (string smtpServer in mxHosts)
        mailer.SmtpServers.Add(new SmtpServer(smtpServer));

    if (mailer.Connect())
    {
        if (mailer.Hello())
        {
            for (int i = 0; i < numOfEmails; i++)
            {
               mailer.Message = new MailMessage();
               // Configure your From, To, Subject etc.
               // with your data

               mailer.Send();
            }
        }

        mailer.Disconnect();
    }
}