I have ispconfig 3.05.3 on ubuntu 12.04.5, last days I notice that ispconfig is sending mails from non existent domains or non existent mail boxes. All the mails are sent from [email protected]. Any idea? thanks
You'd need to determine where the mail is coming from, eg. probably either a compromised mail account or a hacked website. Mail accounts are easy to fix, just change the password. Hacked websites would need updated/cleaned up. There are quite a few other threads you can find on this topic which can give you some things to check, eg. this one recently: https://www.howtoforge.com/community/threads/spam-problem-from-non-existent-addresses.73317/
