Home / server / Questions / 147445
In Process
JL.
Asked: 2010-06-03 05:04:31 +0800 CST

SMTP 552 4.3.1 Session size exceeds fixed maximum session size

  • 772

I'm having a frustrating problem with one of our clients who is running an exchange SMTP server.

I have an emailing component that is written in .net and I've specifically used Mono DLL's to ensure that the email component sends the ELO and QUIT command for each message it sends.

Each mail I send will never exceed 10MB's including attachments, which is lower than the session size value set in the clients exchange configuration.

Still the problem persists. Any ideas where to look?

exchange smtp

2 Answers

  1. Any file attachments will grow by a significant percentage when encoded into base64, so make sure there's at least 30% head room between file size for all attachments and max session size.

    wikipedia on base64:

    Thus, the actual length of MIME-compliant Base64-encoded binary data is usually about 137% of the original data length

    It also Might be worthwhile running wireshark on the server or client to check the content length exactly and ensure that it's actually doing what you told it to do and disconnecting

    • 3

  2. How many emails are you sending in a single session? Do you disconnect and reconnect for each mail? I've heard this happens if you have too many messages in one connection.

    What are the email size limits on the mail server set to? Quota sizes? etc.?

    And what exactly are the error messages on the logs of the Exchange server saying, if anything?

    • 2