It doesn't. Well, not as far as I know.
Ok, you are right, moodle doesn't, quick mail does, I should ask there, thank you.
Not mail server problem,
the problem is , if some users use the email that is not exist or their mail box is full, then moodle will log a "Email failed to send" log in to the database every minute.
the problem is , if some users use the email that is not exist or their mail box is full, then moodle will log a "Email failed to send" log in to the database every minute.
the log is like :
7 February 2020, 9:18 PM SENDER RECEIVER System System Email failed to send Failed to send an email from the user with id '17953' to the user with id '20291' due to the following error: "SMTP Error: The following recipients failed: USEREMAIL: : Recipient address rejected: Domain not found ". cli
You say, Moodle keep on trying even if the sending fails, 5XX codes? Core Moodle does not - that is the correct behaviour. So your problem must be with Quick_mail. Ask its developers, forum General plugins(?)
Ya, I think Quickmail does that not moodle, I will try to modify the code of quickmail to stop do that, thank you.
What is the best alternative for Quickmail?