Why am I seeing failed Postfix logins?
I'm seeing a bunch of failed logins for my Postfix service even though it's still mid-installation. Why are these happening? And how do I stop them?
This is a relatively normal part of running an online server - hackers will attempt to get into your system any way they can. The majority of these attempts are likely coming from bots which have scanned your Linode and found open ports.
You're going to want to make sure you properly secure your server, including all of the running services. Our email guide covers how this is done for email-related systems such as Postfix.
A good way to block these attacks is to use fail2ban, which is covered in the following article. This will automatically block any failed login attempts after a set amount of time. I prefer 3 failed logins and then a lifetime ban, but this can be adjusted as needed.
We also have a general guide on securing your Linode. By following this you will be able to withstand pretty much any attack against your system. Pay particular attention to the public key authentication section.