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

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 7:30 PM UTC

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 7:30 PM UTC

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’re continuing to work closely with the third-party service to delist additional IP addresses that are being blocked on the third-party’s anti-spam service. Since introducing anti-spam optimization changes, we’ve observed a reduction in the total number of blocked instances and we’re continuing to implement additional anti-spam optimization changes to mitigate impact further.

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: Friday, January 19, 2024, at 7:30 PM UTC

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've deployed some anti-spam optimization changes and have seen positive results in terms of reduced counts related to delisted IPs. We're continuing to internally validate additional anti-spam optimization changes, as well as work in conjunction with the third-party service to delist IP addresses which are 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: Thursday, January 18, 2024, at 7:30 PM UTC

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're continuing to work in conjunction with the third-party service to delist IP addresses which are blocked on the third-party's anti-spam service, In parallel, we're continuing to develop the anti-spam optimizations for long-term mitigation, which we'll provide a timeline for deployment to the affected environment when available.

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 17, 2024, at 11:30 PM UTC

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're working in conjunction with the third-party service to delist a number of the IP addresses which are blocked on the third-party's anti-spam service. While this has successfully mitigated the issue for a majority of users, we're developing a series of anti-spam system optimizations to further address the issue. We'll share more details regarding the timeline for these optimizations once they become available.

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: Thursday, January 11, 2024, at 11:30 PM UTC

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're continuing to evaluate the traffic patterns and are working with the third-party service to determine the correct course of action to remediate the impact.

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: Tuesday, January 9, 2024, at 11:30 PM UTC

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: Our collaborative analysis with the third-party service has confirmed that some of the third-party's blocks were intentional; however, we're continuing to work with the provider to ensure legitimate mail is delivered as expected. We're also reviewing anti-spam changes that could be implemented on our side to further resolve the issue.

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 8, 2024, at 11:00 PM UTC

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've received reports that some users may be unable to send or receive email messages due to a third-party anti-spam service listing our IP addresses within their service. We're working with the third-party anti-spam service to better understand why our IP addresses have been listed and what actions need to be taken to resolve this issue.

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: Friday, January 5, 2024, at 11:00 PM UTC