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Asked: 2026-05-11T00:11:04+00:00

Hey all. We’re sending quite a few emails (around 23k) using IIS6 SMTP service

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Hey all. We’re sending quite a few emails (around 23k) using IIS6 SMTP service and receive about 7-8 error messages each time. The stack trace is:

System.Net.Mail.SmtpException: Exceeded storage allocation. The server response was: 4.3.1 Session size exceeds fixed maximum session size    at System.Net.Mail.DataStopCommand.CheckResponse(SmtpStatusCode statusCode, String serverResponse)    at System.Net.Mail.DataStopCommand.Send(SmtpConnection conn)    at System.Net.Mail.SmtpConnection.OnClose(Object sender, EventArgs args)    at System.Net.ClosableStream.Close()    at System.Net.Mail.MailWriter.Close()    at System.Net.Mail.SmtpClient.Send(MailMessage message)

Our SMTP configuration is:

Limit message size: 2048k Limit session size: 20240k Limit # of messages per connection: 20 Limit # of recipients per message: 100

Is it as simple as adjusting the session size? If so, what is recommended? Should we just uncheck limit session size?

I don’t claim to be an expert with SMTP setups, but if I can eliminate these error messages, that would seem like a step forward.

Thanks

Jim

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  1. Jim, this seems like it’s running out of disk space storing all the temp queue files to be sent out. Which is why you only see the error a couple times. As it sends the messages, I’m sure it cleans up the temp files, making room for more. Keep in mind that you can send emails MANY, MANY times faster than the SMTP server can deliver them to the world, and thus, you can create a hell of a queue.

    The failed deliveries don’t help either…

    I would look at a config option that sets the limit of how much drive space it’s allowed to use for temp files.

    The session limit is probably only for a said CONNECTION to your SMTP server, and only allows so much data to be pumped into your SMTP server before it says, ‘woah buddy..’.

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