Bugzilla

Alexander wrote:
>The user then had to re-login into the Microsoft account. (Though I am not sure, whether this other error might be related to the try build interfering with the profile of the normal Thunderbird 115.)

I wrote:
>Not sure I understand what this means. Did the user get locked out from sending more SMTP to MS similar to what I saw with GMX?

I just now looked in my email Inbox and see the logs you sent, 3.txt and 0.txt.
0.txt shows what happens when 25 messages are sent, each on it's own connection to exchange. TB popped up a message about timeout for the 26th message but it looks like, from the log, that the problem was first caused by a failure to login via OAUTH2. For this, I don't see how a retry would help since TB would just keep trying to use the now invalidated oauth2 token and fail again. So maybe the user really was somehow locked out and had to ask for the account to be unlocked.
But this begs the question, why did the oauth2 login fail on the 26th message? I don't know if it's something about oauth or some other problem detected by the exchange server. I did find that the default max message rate for exchange is 30 messages per minute. But only 25 were sent before it failed and I don't know the time span of the log since timestamps aren't included.

Looking at the 3.txt log, it's as you describe in comment 0. I also found that the default max session time for exchange is 10 minutes so that explains it. So if I change the patch to also handle 4xx errors on RCPT TO response too (not just MAIL FROM) it should handle the 10 minute limit.
But a pref (and ideally a UI) to limit the connection time would also be useful (as you point out in the email).

Here are some links that discuss the 10 minute max session time and the 30 messages per minute rate limit for exchange:
https://stackoverflow.com/questions/41769476/send-mailmessage-returns-4-4-1-connection-timed-out-every-10-minutes
https://learn.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/exchange-online-limits?redirectedfrom=MSDN#sending-limits-1

Alexander wrote:
>The user then had to re-login into the Microsoft account. (Though I am not sure, whether this other error might be related to the try build interfering with the profile of the normal Thunderbird 115.)

I wrote:
>Not sure I understand what this means. Did the user get locked out from sending more SMTP to MS similar to what I saw with GMX?

I just now looked in my email Inbox and see the logs you sent, 3.txt and 0.txt.
0.txt shows what happens when 25 messages are sent, each on it's own connection to exchange. TB popped up a message about timeout for the 26th message but it looks like, from the log, that the problem was first caused by a failure to login via OAUTH2. For this, I don't see how a retry would help since TB would just keep trying to use the now invalidated oauth2 token and fail again. So maybe the user really was somehow locked out and had to ask for the account to be unlocked.
But this begs the question, why did the oauth2 login fail on the 26th message? I don't know if it's something about oauth or some other problem detected by the exchange server. I did find that the default max message rate for exchange is 30 messages per minute. But only 25 were sent before it failed and I don't know the time span of the log since timestamps aren't included.

Looking at the 3.txt log, it's as you describe in comment 0. I also found that the default max session time for exchange is 10 minutes so that explains it. So if I change the patch to also handle 4xx errors on RCPT TO response too (not just MAIL FROM) it should handle the 10 minute limit.
But a pref (and ideally a UI) to limit the connection time would also be useful (as you point out in the email).
In addition a pref/UI item to introduce a delay between messages to possibly limit the send rate would be helpful.

Here are some links that discuss the 10 minute max session time and the 30 messages per minute rate limit for exchange:
https://stackoverflow.com/questions/41769476/send-mailmessage-returns-4-4-1-connection-timed-out-every-10-minutes
https://learn.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/exchange-online-limits?redirectedfrom=MSDN#sending-limits-1