Message Size Limit and Exchange NDR message

Hi all.

I wish to know if it is possible to change the inbound messaze size limit.

We have an Exchange Server that cannot send back the NDR message when the size limit is reached.

So people never know if a message has been delivered or not to the recipient.

Any solution?

  • Hi  

    The Inbound message Size limit can not be changed. Would you share more details regarding the issue you're facing? We can try to work for a fix for that.

  • In reply to Jaydeep:


    we have the same problem. Our Exchange 2010 server has a mailsize limit of 20 Mb. The mail server that try to send us a mail more large, receive from Sophos Gateway an ok message, therefore for the sender thinks that the mail was received correctly.

    When the Sophos Gateway try to send the mail to our exchange server, it receive the message '5.3.4 Message size exceeds fixed maximum message size'.

    The problem is that the sender doesn't receive any NDR.

    Can you help us ?

    Thank you

  • In reply to Roberto Bianchi1:

    Yes, the problem is identical.

    Our Exchange has a size limit on inbount set to 20MB, when the Sophos Mail has a size limit of 50.

    When users send message sized 30MB, the NDR message is generated by Exchange, but not received from sender.... 

  • In reply to Andrea Rinaldi:

    I enabled the transport connector log and i have found the transaction between our Exchange server and Sophos with the error 5.3.4:


    2019-12-31T12:41:58.111Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,0,,,+,,
    2019-12-31T12:41:58.111Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,1,,,*,SMTPSubmit SMTPAcceptAnySender SMTPAcceptAuthoritativeDomainSender AcceptRoutingHeaders,Set Session Permissions
    2019-12-31T12:41:58.111Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,2,,,>,"220 <OUR MAIL SERVER> Microsoft ESMTP MAIL Service ready at Tue, 31 Dec 2019 13:41:57 +0100",
    2019-12-31T12:41:58.127Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,3,,,<,EHLO,
    2019-12-31T12:41:58.127Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,4,,,>,250-<OUR MAIL SERVER>.<OUR DOMAIN.LAN> Hello [],
    2019-12-31T12:41:58.127Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,5,,,>,250-SIZE,
    2019-12-31T12:41:58.127Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,6,,,>,250-PIPELINING,
    2019-12-31T12:41:58.127Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,7,,,>,250-DSN,
    2019-12-31T12:41:58.127Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,8,,,>,250-ENHANCEDSTATUSCODES,
    2019-12-31T12:41:58.127Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,9,,,>,250-STARTTLS,
    2019-12-31T12:41:58.127Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,10,,,>,250-AUTH NTLM,
    2019-12-31T12:41:58.127Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,11,,,>,250-8BITMIME,
    2019-12-31T12:41:58.127Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,12,,,>,250-BINARYMIME,
    2019-12-31T12:41:58.127Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,13,,,>,250 CHUNKING,
    2019-12-31T12:41:58.142Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,14,,,<,MAIL FROM:<SENDER MAIL ADDRESS@GMAIL.COM> SIZE=33114769,
    2019-12-31T12:41:58.142Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,15,,,*,Tarpit for '0.00:00:05',
    2019-12-31T12:42:03.150Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,16,,,>,552 5.3.4 Message size exceeds fixed maximum message size,
    2019-12-31T12:42:03.166Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,17,,,<,RSET,
    2019-12-31T12:42:03.166Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,18,,,*,Tarpit for '0.00:00:05',
    2019-12-31T12:42:08.173Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,19,,,>,250 2.0.0 Resetting,
    2019-12-31T12:42:08.189Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,20,,,<,QUIT,
    2019-12-31T12:42:08.189Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,21,,,>,221 2.0.0 Service closing transmission channel,
    2019-12-31T12:42:08.189Z,<OUR MAIL SERVER>\Default <OUR MAIL SERVER>,08D78D67A2EC9746,22,,,-,,Local

    But i didn't find any trace about NDR message and/or a log that show that it was blocked by Sophos. Have you found it ?