214-379-4200 - Business Only support@avaren.com

This week, there have been multiple reports from customers of intermittent failures when sending outbound mail from the O365 system. Microsoft (and a third party spam filter provider) are both aware of the situation and working on it. Should you receive this error (shown immediately below) in coming days, please wait 15-20 minutes and try to send your e-mail again. The affected servers are part of an apparent round-robin, and thus it is possible for outbound mail to use a different server each time.

 

 

 

 

A Recent Update From Microsoft On This Matter

Some users may be unable to send or receive email messages, and receive a Non-Delivery Report (NDR) when sending

Affected services: Exchange Online

Issue type: Incident

Issue origin: Microsoft

Status: Service Degradation

User impact: Users may be unable to send or receive email messages, and receive an NDR with a 550 or 554 error code when sending.

All updates

Jan 22, 2024, 12:22 PM CST Title: Some users may be unable to send or receive email messages, and receive a Non-Delivery Report (NDR) when sending User impact: Users may be unable to send or receive email messages, and receive an NDR with a 550 or 554 error code when sending. More info: This issue only occurs if either the sender or user who is receiving the message is utilizing a specific third-party anti-spam service. Senders receive the NDR which states that the message has been rejected due to a 550 or 554 error code and that their host IP address is listed on the third-party anti-spam service. The error messages state “550 5.7.350 Remote server returned message detected as spam”, “554 5.7.1 Service unavailable; Client host [xxx.xxx.xxx.xxx] blocked”, or “‎550 5.7.1 This email was rejected because it violates our security policy.” Current status: We’ve implemented additional rule changes intended to further reduce outbound spam patterns, which has produced a reduction in the number of blocked instances. We’re continuing our collaboration with the third-party service to delist affected IP addresses that are being blocked on the third-party’s anti-spam service. Scope of impact: This issue may affect any user’s mail flow if the recipient is leveraging a specific third-party anti-spam service to filter email messages. Next update by: Wednesday, January 24, 2024 at 1:30 PM CST

Jan 19, 2024, 12:23 PM CST Title: Some users may be unable to send or receive email messages and receive a Non-Delivery Report (NDR) User impact: Users may be unable to send or receive email messages and receive a NDR with a 550 or 554 error code. More info: This issue only occurs if either the sender or user who is receiving the message is utilizing a specific third-party anti-spam service. Senders receive the NDR which states that the message has been rejected due to a 550 or 554 error code and that their host IP address is listed on the third-party anti-spam service. The error messages state “550 5.7.350 Remote server returned message detected as spam”, “554 5.7.1 Service unavailable; Client host [xxx.xxx.xxx.xxx] blocked”, or “‎550 5.7.1 This email was rejected because it violates our security policy.” Current status: We continue to collaborate with the third-party service to delist additional IP addresses that are being blocked on the third-party’s anti-spam service. In parallel, we continue to analyze outbound spam patterns and implement targeted rules and optimizations for these patterns, which has produced a reduction in the number of blocked instances. Scope of impact: This issue may affect any user’s mail flow if the recipient is leveraging a specific third-party anti-spam service to filter email messages. Next update by: Monday, January 22, 2024 at 1:30 PM CST

 

ML/jk

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