When email is sent by my SMTP Relay (or Forward in POP3 downloader) module I see errors in the log saying "552 4.3.1 Message size exceeds fixed maximum message" or "552 5.3.4 Message size exceeds fixed maximum message". This is typically when sending email to Microsoft Exchange. What can I do?
Those errors are being reported from the next server, the one Hexamail is trying to send the email onwards to. In the log just above it should say which server is being contacted. Typically this error message is generated by message limits set in Microsoft ISA server, Microsoft Exchange or Symantec Antivirus SMTP gateway.
Setting the maximum message size is of course different in almost every single version of Exchange. Follow the links below to find out how to do so in each version: