We are seeing odd behavior for emails sent to our on-premises Exchange 2013 server.
Mails sent from Outlook.com with at least one invalid address on the To field are bouncing back to the sender as undeliverable to all addresses...even the valid ones, and the valid recipients do not receive the email. The same mail sent from Gmail does bounce back indicating that it could not be delivered to the recipient and the valid recipient(s) do get the emails.
The SMTP protocol logs for both are below. Any idea why the behavior would differ? Note: This is causing issues for us as emails from Microsoft employees behave the same way.
From what I can see in the logs, it looks like the problem is that Outlook.com is using the same SessionID for both recipients, so when the User unknown goes back it has no way of knowing which recipient was invalid and the mail is rejected for all senders.
I could be wrong, but this seems like a fundamental problem with how Outlook (and as a result...Microsoft as a whole) is sending mails.
From Outlook.com:
2013-11-11T22:21:36.890Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,6,192.168.100.20:25,65.55.111.154:22793,>,250-PIPELINING, 2013-11-11T22:21:36.890Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,7,192.168.100.20:25,65.55.111.154:22793,>,250-DSN, 2013-11-11T22:21:36.890Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,8,192.168.100.20:25,65.55.111.154:22793,>,250-ENHANCEDSTATUSCODES, 2013-11-11T22:21:36.890Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,9,192.168.100.20:25,65.55.111.154:22793,>,250-STARTTLS, 2013-11-11T22:21:36.890Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,10,192.168.100.20:25,65.55.111.154:22793,>,250-X-ANONYMOUSTLS, 2013-11-11T22:21:36.890Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,11,192.168.100.20:25,65.55.111.154:22793,>,250-AUTH NTLM, 2013-11-11T22:21:36.890Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,12,192.168.100.20:25,65.55.111.154:22793,>,250-X-EXPS GSSAPI NTLM, 2013-11-11T22:21:36.890Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,13,192.168.100.20:25,65.55.111.154:22793,>,250-8BITMIME, 2013-11-11T22:21:36.890Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,14,192.168.100.20:25,65.55.111.154:22793,>,250-BINARYMIME, 2013-11-11T22:21:36.890Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,15,192.168.100.20:25,65.55.111.154:22793,>,250-CHUNKING, 2013-11-11T22:21:36.890Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,16,192.168.100.20:25,65.55.111.154:22793,>,250 XRDST, 2013-11-11T22:21:36.921Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,17,192.168.100.20:25,65.55.111.154:22793,<,MAIL FROM:<jon.rauschenberger@outlook.com> SIZE=149944, 2013-11-11T22:21:36.921Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,18,192.168.100.20:25,65.55.111.154:22793,*,08D0AB95076886A8;2013-11-11T22:21:36.874Z;1,receiving message 2013-11-11T22:21:36.921Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,19,192.168.100.20:25,65.55.111.154:22793,>,250 2.1.0 Sender OK, 2013-11-11T22:21:36.937Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,20,192.168.100.20:25,65.55.111.154:22793,<,RCPT TO:<validaddress@claritycon.com>, 2013-11-11T22:21:36.937Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,21,192.168.100.20:25,65.55.111.154:22793,<,RCPT TO:<invalidaddress@claritycon.com>, 2013-11-11T22:21:36.937Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,22,192.168.100.20:25,65.55.111.154:22793,>,250 2.1.5 Recipient OK, 2013-11-11T22:21:36.937Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,23,192.168.100.20:25,65.55.111.154:22793,>,250 2.1.5 Recipient OK, 2013-11-11T22:21:36.968Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,24,192.168.100.20:25,65.55.111.154:22793,<,DATA, 2013-11-11T22:21:36.968Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,25,192.168.100.20:25,65.55.111.154:22793,>,354 Start mail input; end with <CRLF>.<CRLF>, 2013-11-11T22:21:38.468Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A9,0,192.168.100.20:25,67.66.142.141:25055,+,, 2013-11-11T22:21:38.468Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A9,1,192.168.100.20:25,67.66.142.141:25055,*,SMTPSubmit SMTPAcceptAnySender SMTPAcceptAuthoritativeDomainSender AcceptRoutingHeaders,Set Session Permissions 2013-11-11T22:21:38.468Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A9,2,192.168.100.20:25,67.66.142.141:25055,>,"220 CC-EXCH-01.clarityinternal.net Microsoft ESMTP MAIL Service ready at Mon, 11 Nov 2013 16:21:38 -0600", 2013-11-11T22:21:38.514Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A9,3,192.168.100.20:25,67.66.142.141:25055,<,EHLO s927-apmail10.ssmhc.com, 2013-11-11T22:21:38.514Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A9,4,192.168.100.20:25,67.66.142.141:25055,>,250-CC-EXCH-01.clarityinternal.net Hello [67.66.142.141], 2013-11-11T22:21:38.514Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A9,5,192.168.100.20:25,67.66.142.141:25055,>,250-SIZE 37748736, 2013-11-11T22:21:38.514Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A9,6,192.168.100.20:25,67.66.142.141:25055,>,250-PIPELINING, 2013-11-11T22:21:38.514Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A9,7,192.168.100.20:25,67.66.142.141:25055,>,250-DSN, 2013-11-11T22:21:38.514Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A9,8,192.168.100.20:25,67.66.142.141:25055,>,250-ENHANCEDSTATUSCODES, 2013-11-11T22:21:38.514Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A9,9,192.168.100.20:25,67.66.142.141:25055,>,250-STARTTLS, 2013-11-11T22:21:38.514Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A9,10,192.168.100.20:25,67.66.142.141:25055,>,250-X-ANONYMOUSTLS, 2013-11-11T22:21:38.530Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,26,192.168.100.20:25,65.55.111.154:22793,*,,Proxy destination(s) obtained from OnProxyInboundMessage event 2013-11-11T22:21:46.403Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,28,192.168.100.20:25,65.55.111.154:22793,>,550 5.1.1 User unknown, 2013-11-11T22:21:46.419Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,29,192.168.100.20:25,65.55.111.154:22793,<,QUIT, 2013-11-11T22:21:46.419Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,30,192.168.100.20:25,65.55.111.154:22793,>,221 2.0.0 Service closing transmission channel, 2013-11-11T22:21:46.419Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886A8,31,192.168.100.20:25,65.55.111.154:22793,-,,Local
From Gmail:
2013-11-11T22:22:23.207Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,3,192.168.100.20:25,209.85.212.48:64290,<,EHLO mail-vb0-f48.google.com, 2013-11-11T22:22:23.207Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,4,192.168.100.20:25,209.85.212.48:64290,>,250-CC-EXCH-01.clarityinternal.net Hello [209.85.212.48], 2013-11-11T22:22:23.207Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,5,192.168.100.20:25,209.85.212.48:64290,>,250-SIZE 37748736, 2013-11-11T22:22:23.207Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,6,192.168.100.20:25,209.85.212.48:64290,>,250-PIPELINING, 2013-11-11T22:22:23.207Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,7,192.168.100.20:25,209.85.212.48:64290,>,250-DSN, 2013-11-11T22:22:23.207Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,8,192.168.100.20:25,209.85.212.48:64290,>,250-ENHANCEDSTATUSCODES, 2013-11-11T22:22:23.207Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,9,192.168.100.20:25,209.85.212.48:64290,>,250-STARTTLS, 2013-11-11T22:22:23.207Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,10,192.168.100.20:25,209.85.212.48:64290,>,250-X-ANONYMOUSTLS, 2013-11-11T22:22:23.207Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,11,192.168.100.20:25,209.85.212.48:64290,>,250-AUTH NTLM, 2013-11-11T22:22:23.207Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,12,192.168.100.20:25,209.85.212.48:64290,>,250-X-EXPS GSSAPI NTLM, 2013-11-11T22:22:23.207Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,13,192.168.100.20:25,209.85.212.48:64290,>,250-8BITMIME, 2013-11-11T22:22:23.207Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,14,192.168.100.20:25,209.85.212.48:64290,>,250-BINARYMIME, 2013-11-11T22:22:23.207Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,15,192.168.100.20:25,209.85.212.48:64290,>,250-CHUNKING, 2013-11-11T22:22:23.207Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,16,192.168.100.20:25,209.85.212.48:64290,>,250 XRDST, 2013-11-11T22:22:23.222Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B7,17,192.168.100.20:25,209.85.212.43:45926,<,MAIL FROM:<jon@rauschenberger.net>, 2013-11-11T22:22:23.222Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B7,18,192.168.100.20:25,209.85.212.43:45926,*,08D0AB95076886B7;2013-11-11T22:22:23.160Z;1,receiving message 2013-11-11T22:22:23.222Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B7,19,192.168.100.20:25,209.85.212.43:45926,>,250 2.1.0 Sender OK, 2013-11-11T22:22:23.238Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,17,192.168.100.20:25,209.85.212.48:64290,<,MAIL FROM:<jon@rauschenberger.net>, 2013-11-11T22:22:23.238Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,18,192.168.100.20:25,209.85.212.48:64290,*,08D0AB95076886B8;2013-11-11T22:22:23.175Z;1,receiving message 2013-11-11T22:22:23.238Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,19,192.168.100.20:25,209.85.212.48:64290,>,250 2.1.0 Sender OK, 2013-11-11T22:22:23.254Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B7,20,192.168.100.20:25,209.85.212.43:45926,<,RCPT TO:<validaddress@claritycon.com>, 2013-11-11T22:22:23.254Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B7,21,192.168.100.20:25,209.85.212.43:45926,>,250 2.1.5 Recipient OK, 2013-11-11T22:22:23.269Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,20,192.168.100.20:25,209.85.212.48:64290,<,RCPT TO:<invalidaddress@claritycon.com>, 2013-11-11T22:22:23.269Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,21,192.168.100.20:25,209.85.212.48:64290,>,250 2.1.5 Recipient OK, 2013-11-11T22:22:23.288Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B7,22,192.168.100.20:25,209.85.212.43:45926,<,DATA, 2013-11-11T22:22:23.288Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B7,23,192.168.100.20:25,209.85.212.43:45926,>,354 Start mail input; end with <CRLF>.<CRLF>, 2013-11-11T22:22:23.301Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,22,192.168.100.20:25,209.85.212.48:64290,<,DATA, 2013-11-11T22:22:23.301Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,23,192.168.100.20:25,209.85.212.48:64290,>,354 Start mail input; end with <CRLF>.<CRLF>, 2013-11-11T22:22:23.332Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B7,24,192.168.100.20:25,209.85.212.43:45926,*,,Proxy destination(s) obtained from OnProxyInboundMessage event 2013-11-11T22:22:23.332Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,24,192.168.100.20:25,209.85.212.48:64290,*,,Proxy destination(s) obtained from OnProxyInboundMessage event 2013-11-11T22:22:23.347Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,25,192.168.100.20:25,209.85.212.48:64290,*,Tarpit for '0.00:00:05', 2013-11-11T22:22:28.362Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,26,192.168.100.20:25,209.85.212.48:64290,>,550 5.1.1 User unknown, 2013-11-11T22:22:28.393Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,27,192.168.100.20:25,209.85.212.48:64290,<,QUIT, 2013-11-11T22:22:28.393Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,28,192.168.100.20:25,209.85.212.48:64290,>,221 2.0.0 Service closing transmission channel, 2013-11-11T22:22:28.393Z,CC-EXCH-01\Default Frontend CC-EXCH-01,08D0AB95076886B8,29,192.168.100.20:25,209.85.212.48:64290,-,,Local