451 4.3.111 Temporary server error. Please try again later MRH1

[AptoSx4]

Hello everybody, we have been using Switf Mailer for a while conected to a mailbox on O365 but since yesterday we are receiving the following error.

Expected response code 250 but got code "451", with message "451 4.3.111 Temporary server error. Please try again later MRH1."

I don´t know what 4.3.111 means... I looked on internet but no results.

We thought at first that our mailbox was with some errors but all appears to be OK ... so we don't know where start...

Has anyone had this error, and how to solve it?

Cheers!

[#2]

@AptoSx4 

Did you or someone else found the root cause for this and ideally a solution?

Best

Sebastian

[#3]

We are also experiencing this same issue not frequently but when we do send emails in batch of size 25 from our application. 

We are also trying to find the root cause of this issue. Please let us know.