I have a linux server (suse 11.2) with postfix on it. I receive all mail, but when a mail has an attachment .doc or .xls I don't receive the mail and after a while the sender gets a message the server has timed out. When I change the extension it does the same, when I send a docx it goes allright, when I zip the doc it also goes allright. In the log-file it says nothing about the timeout.
The timeout is
sending server connects to your postfix server:
your server at this point is checking the attachment, anti-virus,anti-spam, etc. but this process takes longer that the sending server is willing to wait.
The connection is severed/terminated due to a connection timeout.