Update
In my case the problem is about our ISP's network, they have some filtering device/software that work incorrectly, then it blocks our large mail to Yahoo.
Dear all
Recently I founded an Exchange Server problem that I cannot know why it happens. I'm working on Exchange Technology since 2000 and this is the first problem that I cannot find any resolution. Please help me if you can.
My new company use a newly implement Exchange Server 2013 (No previous version in this company).
Our sending IP is not listed in any RBL, I have reverse DNS record that matched the sending IP (also matched MX record), Sending IP is on SPF record.
Send connector is using MX's DNS name in HELO message (Force HELO is enabled).
I can send mail to all major mail provider (Gmail, Outlook.com and others) except the Yahoo.
In many testing I founded most of smaller mail (0-3 MB) can send to Yahoo without any problems, but bigger mail (In the test I use 10MB attachment) can't.
I check all my firewall/content filtering gateway, no filtering settings or something like that is founded. For Exchange Server, no message size restriction is configured and no special configuration for Yahoo.
I also test my configuration with Exchange Remote Connectivity Analyzer (Outbound SMTP) and no problem founded.
I check the SMTP log and found this error
HandleError has encountered a suspicious connection reset from a remote, non-mailbox transport server (will retry in 00:10:00)
The full log is (I change the real domain and some privacy data)
2013-07-22T16:30:04.335Z,Mail Connector,08D053603E76D1D8,0,,98.136.216.26:25,*,,attempting to connect
2013-07-22T16:30:04.351Z,Mail Connector,08D053603E76D1D8,1,192.168.1.13:32418,98.136.216.26:25,+,,
2013-07-22T16:30:04.834Z,Mail Connector,08D053603E76D1D8,2,192.168.1.13:32418,98.136.216.26:25,<,220 mta1075.mail.gq1.yahoo.com ESMTP YSmtpProxy service ready,
2013-07-22T16:30:04.834Z,Mail Connector,08D053603E76D1D8,3,192.168.1.13:32418,98.136.216.26:25,>,HELO mymail.com,
2013-07-22T16:30:05.255Z,Mail Connector,08D053603E76D1D8,4,192.168.1.13:32418,98.136.216.26:25,<,250 mta1075.mail.gq1.yahoo.com,
2013-07-22T16:30:05.255Z,Mail Connector,08D053603E76D1D8,5,192.168.1.13:32418,98.136.216.26:25,*,,sending message with RecordId 12309376270368 and InternetMessageId <f6ca2855b4e549969e9d71d7dc7302da@srv1.mymail.com>
2013-07-22T16:30:05.255Z,Mail Connector,08D053603E76D1D8,6,192.168.1.13:32418,98.136.216.26:25,>,MAIL FROM:<usr1@mymail.com>,
2013-07-22T16:30:05.521Z,Mail Connector,08D053603E76D1D8,7,192.168.1.13:32418,98.136.216.26:25,<,250 sender <usr1@mymail.com> ok,
2013-07-22T16:30:05.521Z,Mail Connector,08D053603E76D1D8,8,192.168.1.13:32418,98.136.216.26:25,>,RCPT TO:<yahoousr@yahoo.com>,
2013-07-22T16:30:05.770Z,Mail Connector,08D053603E76D1D8,9,192.168.1.13:32418,98.136.216.26:25,<,250 recipient <yahoousr@yahoo.com> ok,
2013-07-22T16:30:06.051Z,Mail Connector,08D053603E76D1D8,10,192.168.1.13:32418,98.136.216.26:25,>,DATA,
2013-07-22T16:30:06.067Z,Mail Connector,08D053603E76D1D8,11,192.168.1.13:32418,98.136.216.26:25,<,354 end data with <CR><LF>.<CR><LF>,
2013-07-22T16:30:10.793Z,Mail Connector,08D053603E76D1D8,12,192.168.1.13:32418,98.136.216.26:25,*,,"HandleError has encountered a suspicious connection reset from a remote, non-mailbox transport server (will retry in 00:10:00)."
2013-07-22T16:30:10.793Z,Mail Connector,08D053603E76D1D8,13,192.168.1.13:32418,98.136.216.26:25,-,,Remote
At present, because we cannot send mail directly to Yahoo, then we send mail to Yahoo via our ISP's relay (we add ISP's relay IP to our SPF record) and it works fine. But for me, this solution is not a good solution because our ISP's relay has some restriction and I'm not sure they will block us or not in the future if their policy changed.
Please help me if you can.
Regards
Jun.