On Thu, Sep 5, 2013 at 3:48 PM, Kwas Lee <leekwas@yahoo.com> wrote:
Could someone please advice as some of sender are unable to send mails to my server when i check the logs i found
2013-09-05 20:31:32 SMTP connection from smtp-sender.com (senderdomain.com) [xx.xx.xx.xx] lost while reading message data (header)
Hi Lee, Smells like path MTU. The connection died at what is probably the first time in the SMTP session that the remote system tried to send you a large, probably 1500 byte packet: the beginning (message header) part of the data portion (the email message headers and body themselves, as opposed to the sender and recipient declarations). This is not the only candidate cause, but that's what my mind jumps to. Try adjusting the TCP Maximum Segment Size on your server. Turn it down to 1200 or so and see if the problem vanishes. If so, somebody's losing ICMP packets. Regards, Bill Herrin -- William D. Herrin ................ herrin@dirtside.com bill@herrin.us 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> Falls Church, VA 22042-3004