![Mail loop between Hybrid and legacy server. 421 4.2.1 Unable to connect or 451 4.4.397 Error communicating with target host or 451 4.7.0 Temporary server error – Modern 365 Mail loop between Hybrid and legacy server. 421 4.2.1 Unable to connect or 451 4.4.397 Error communicating with target host or 451 4.7.0 Temporary server error – Modern 365](https://praveenkumare.files.wordpress.com/2021/07/1.png)
Mail loop between Hybrid and legacy server. 421 4.2.1 Unable to connect or 451 4.4.397 Error communicating with target host or 451 4.7.0 Temporary server error – Modern 365
![🐘 @dergrobi@nrw.social on Twitter: "Since #Microsoft turned on #IPv6 for their outlook[,]com mail servers this morning, the servers respond with "451 4.7.500 Server busy" when trying to deliver e-mail via IPv6. That's 🐘 @dergrobi@nrw.social on Twitter: "Since #Microsoft turned on #IPv6 for their outlook[,]com mail servers this morning, the servers respond with "451 4.7.500 Server busy" when trying to deliver e-mail via IPv6. That's](https://pbs.twimg.com/media/FgBzAofWAAAjeD3.png)
🐘 @dergrobi@nrw.social on Twitter: "Since #Microsoft turned on #IPv6 for their outlook[,]com mail servers this morning, the servers respond with "451 4.7.500 Server busy" when trying to deliver e-mail via IPv6. That's
RESOLVED Advisory: For some Sophos Central Customers, the Directory Services> Azure AD Configuration page will not load - an error can be seen "Something went wrong. Please try again later "
![Office 365 throttling 451 4.7.500 Server busy. Please try again later from IPADRESS (AS780082) : r/Office365 Office 365 throttling 451 4.7.500 Server busy. Please try again later from IPADRESS (AS780082) : r/Office365](https://preview.redd.it/eou1gj4z9s161.jpg?width=1214&format=pjpg&auto=webp&s=02a56a1c98247c539da232fc3e4e59c32ff692a7)
Office 365 throttling 451 4.7.500 Server busy. Please try again later from IPADRESS (AS780082) : r/Office365
![How can I fix the error: milter-reject: DATA 451 4.7.1 Service unavailable - try again later? - Knowledgebase - Danami How can I fix the error: milter-reject: DATA 451 4.7.1 Service unavailable - try again later? - Knowledgebase - Danami](https://www.danami.com/clients/images/kb/79_2020-11-06_02h45_39.png)
How can I fix the error: milter-reject: DATA 451 4.7.1 Service unavailable - try again later? - Knowledgebase - Danami
![Microsoft Outlook on Twitter: "@patphobos Hi, Patrice. Please try troubleshooting with the steps provided in this thread: https://t.co/6cQ5UhAsM0. Let us know if this helps!" / Twitter Microsoft Outlook on Twitter: "@patphobos Hi, Patrice. Please try troubleshooting with the steps provided in this thread: https://t.co/6cQ5UhAsM0. Let us know if this helps!" / Twitter](https://pbs.twimg.com/media/DdYlWt3X0AA3QcO.jpg)
Microsoft Outlook on Twitter: "@patphobos Hi, Patrice. Please try troubleshooting with the steps provided in this thread: https://t.co/6cQ5UhAsM0. Let us know if this helps!" / Twitter
![FR: Insight for rising number of deferred mails (#319) · Issues · Lightmeter / ControlCenter · GitLab FR: Insight for rising number of deferred mails (#319) · Issues · Lightmeter / ControlCenter · GitLab](https://gitlab.com/uploads/-/system/project/avatar/17017123/gitlab-1.png)