SMTP failing to with suspicious connection error LED=450 4.4.318 Connection was closed abruptly (Sus

Copper Contributor

Yesterday we had an issue with an old DNS record in our system. We deployed a new faxcore server with the same IP address as the old server. The person doing this did not delete the old DNS entry which the PTR record was pointing to the old server FQDN. I deleted the old DNS record freeing up the PTR record. I then updated the new DNS record to update the PTR record to point to the new FQDN. Immeadiately we saw faxes start going through. More than 12 hours later we have some that still retrying with the same error. Others have sent faxes to the same number with success. Here are two of the entries I'm looking at.


2023-06-07T14:13:25.279Z,,<ExchangeServer,<FaxCoreIP_Address>,Retrying due to suspicious connection reset.Progressive backoff retry time of: 00:10:00,Simfax,SMTP,DEFER,116848880255142,<email address removed for privacy reasons>,ff714c12-b24a-4454-47de-08db66b08d5c,email address removed for privacy reasons,'[{LED=450 4.4.318 Connection was closed abruptly (SuspiciousRemoteServerError)};{MSG=};{FQDN=<FaxCoreIP_Address>};{IP=<FaxCoreIP_Address>};{LRT=6/7/2023 2:09:44 PM}]',739847,1,,,ATTN POA / Address change request included,<user_email>,<user_email>,2023-06-07T14:23:25.279Z,Incoming,,,,S:Microsoft.Exchange.Transport.MailRecipient.RequiredTlsAuthLevel=Opportunistic;S:IsSmtpResponseFromExternalServer=False;S:RecipientsAlreadySmtpDeferLogged=true;S:DeliveryPriority=Normal;S:AccountForest=<FQDN_Domain>,Email,21412387-c548-4368-684a-08db67615bce,15.01.2507.023


Good fax:

023-06-07T14:11:33.582Z,,,,V-EXCH16-P,No suitable shadow servers,,SMTP,HAREDIRECTFAIL,116939074568192,<email address removed for privacy reasons>,41f0a756-cadc-4d95-5a21-08db67611939,email address removed for privacy reasons,,12001,1,,,Test,<User_Email>,<User_email>,,Incoming,,,,S:DeliveryPriority=Normal;S:AccountForest=<FQDN_Domain>,Email,9a0d263d-73e1-4636-bd35-08db6761193a,15.01.2507.023


I either need to clear the queue for these users or figure out a way to resolve the Supicious 

1 Reply
best response confirmed by bigmaneric973 (Copper Contributor)
This has been resolved. The issue was with our underlying infrastructure that had an issue. Migrating the server and resetting the socket cleared the problem.

Thank you.