Sudden SMTP send failure to smtp.office365 dot com

%3CLINGO-SUB%20id%3D%22lingo-sub-2695263%22%20slang%3D%22en-US%22%3ESudden%20SMTP%20send%20failure%20to%20smtp.office365%20dot%20com%3C%2FLINGO-SUB%3E%3CLINGO-BODY%20id%3D%22lingo-body-2695263%22%20slang%3D%22en-US%22%3E%3CDIV%3E%3CDIV%20class%3D%22frameless%22%3E%3CDIV%20class%3D%22%22%3E%3CDIV%20class%3D%22sui-opt-in%20root-post%20post%20%20%20my-post%22%3E%3CDIV%3E%3CDIV%20class%3D%22mceNonEditable%20lia-copypaste-placeholder%22%3E%26nbsp%3B%3C%2FDIV%3E%3CP%3EWe%20use%20BMC%20Track-It%20and%20we%20have%20it%20configured%20to%20send%20outbound%20emails%20to%20smtp.office365.com.%20This%20has%20worked%20since%202017.%20We%20use%20port%20587%20and%20SSL%20with%20authentication.%20The%20server%20runs%20Windows%20Server%202016.%20About%20a%20week%20ago%2C%20emails%20stopped%20sending.%20The%20email%20test%20button%20in%20Track-It%20results%20with%26nbsp%3B%26nbsp%3B%20--%20Failure%20sending%20mail.%20%5BSystem.Net.Mail.SmtpException%5D%3CBR%20%2F%3E%26nbsp%3B%20--%20Unable%20to%20read%20data%20from%20the%20transport%20connection%3A%20net_io_connectionclosed.%20%5BSystem.IO.IOException%5D.%3C%2FP%3E%3CP%3E%26nbsp%3B%3C%2FP%3E%3CP%3EA%20Powershell%20test%20comes%20back%20with%20a%20similar%20result%3A%3C%2FP%3E%3CP%3E%3A%20Unable%20to%20read%20data%20from%20the%20transport%20connection%3A%20net_io_connectionclosed.%3C%2FP%3E%3CP%3E%26nbsp%3B%3C%2FP%3E%3CP%3EWireshark%20shows%20success%20on%20Win10%20and%20Server%202016%20including%20this%20Track-It%20server%3A%3C%2FP%3E%3CP%3E%3CSPAN%20class%3D%22lia-inline-image-display-wrapper%20lia-image-align-inline%22%20image-alt%3D%221.jpg%22%20style%3D%22width%3A%20999px%3B%22%3E%3CIMG%20src%3D%22https%3A%2F%2Ftechcommunity.microsoft.com%2Ft5%2Fimage%2Fserverpage%2Fimage-id%2F306420i40400C4AA359F792%2Fimage-size%2Flarge%3Fv%3Dv2%26amp%3Bpx%3D999%22%20role%3D%22button%22%20title%3D%221.jpg%22%20alt%3D%221.jpg%22%20%2F%3E%3C%2FSPAN%3E%3C%2FP%3E%3CP%3E%26nbsp%3B%3C%2FP%3E%3C%2FDIV%3E%3CP%3EThe%20server%20is%20fully%20patched.%26nbsp%3B%3C%2FP%3E%3CP%3EBMC%20and%20Microsoft%20seem%20stumped.%3C%2FP%3E%3CP%3ESince%20this%20was%20working%20fine%20and%20stopped%20one%20day%20without%20explanation%2C%20I%20assume%20Microsoft%20changed%20something%20on%20the%20smtp.office365.com%20servers.%3C%2FP%3E%3CP%3EAny%20ideas%3F%20Thanks!%3C%2FP%3E%3CP%3E%3CBR%20%2F%3E%3CBR%20%2F%3E%3C%2FP%3E%3CDIV%20class%3D%22footer%22%3E%26nbsp%3B%3C%2FDIV%3E%3C%2FDIV%3E%3C%2FDIV%3E%3C%2FDIV%3E%3C%2FDIV%3E%3C%2FLINGO-BODY%3E%3CLINGO-LABS%20id%3D%22lingo-labs-2695263%22%20slang%3D%22en-US%22%3E%3CLINGO-LABEL%3EAdmin%3C%2FLINGO-LABEL%3E%3CLINGO-LABEL%3EOffice%20365%3C%2FLINGO-LABEL%3E%3CLINGO-LABEL%3EOffice%20365%20Network%20Connectivity%3C%2FLINGO-LABEL%3E%3C%2FLINGO-LABS%3E%3CLINGO-SUB%20id%3D%22lingo-sub-2696719%22%20slang%3D%22en-US%22%3ERe%3A%20Sudden%20SMTP%20send%20failure%20to%20smtp.office365%20dot%20com%3C%2FLINGO-SUB%3E%3CLINGO-BODY%20id%3D%22lingo-body-2696719%22%20slang%3D%22en-US%22%3EMake%20sure%20you're%20using%20TLS1.2%20and%20that%20basic%20auth%20isnt%20being%20blocked%2FSMTP%20client%20authentication%20is%20enabled%20for%20the%20user%2Fmailbox%20you're%20using.%3C%2FLINGO-BODY%3E
New Contributor
 

We use BMC Track-It and we have it configured to send outbound emails to smtp.office365.com. This has worked since 2017. We use port 587 and SSL with authentication. The server runs Windows Server 2016. About a week ago, emails stopped sending. The email test button in Track-It results with   -- Failure sending mail. [System.Net.Mail.SmtpException]
  -- Unable to read data from the transport connection: net_io_connectionclosed. [System.IO.IOException].

 

A Powershell test comes back with a similar result:

: Unable to read data from the transport connection: net_io_connectionclosed.

 

Wireshark shows success on Win10 and Server 2016 including this Track-It server:

1.jpg

 

The server is fully patched. 

BMC and Microsoft seem stumped.

Since this was working fine and stopped one day without explanation, I assume Microsoft changed something on the smtp.office365.com servers.

Any ideas? Thanks!



2 Replies
Make sure you're using TLS1.2 and that basic auth isnt being blocked/SMTP client authentication is enabled for the user/mailbox you're using.
Client auth is used. How do I set TLS 1.2 in win server 2016?