Atomicorp

I keep getting that error in my log files full error is as follows: This is the default install from plesk of postfix postfix.x86_64 2:2.3.3-2.1.el5_2

Doesn't seem to be causing issues with mail being sent or received but I would like to solve this issue so it doesn't fill up the log.

This is quite an old post, but as it is the first link that I found when search for more information about this error, I thought I would post here.

The error that is being posted to your logs indicates that someone tried authenticating with postfix but their details were not found. If you are get lots of this, then there is probably a spambot (most likely several) trying brute force email accounts so that it can send spam via your server.

It is nothing to overly concerned about, but if it is causing you problems (or you just want to put a stop to it) - you may want check out something like Fail2Ban.