Hello all.
I have a couple of questions that i would like an answer to.

I have Postfix, Dovecot and PostfixAdmin up and running without a single error popping up in the logs and everything is working as it is suppose to. I can receive mails and send mails both on the local network and on the internet. When on the local network no authentication is needed for relaying mails with Postfix. When getting mails i have to log in with a username and password to get my mails.

First questions is. Can i use this as production server, or better put. Should i add something more to make it more secure to use over the internet before i release it outside the local network? And if so what?

I'm using plain text, I think to transport the user and password when logging in which is a bit scary, how do i know if I am?

I know I should install a virus scanner and maybe some sort of spam remover and I will after i feel that this is up and running production wise.

Thank you in advance for taking your time to help me.

I don't have experience with mail setups but I'd definately add spam removing to it and perhaps anti-virus things.

You should check out how to add STARTTLS support for postfix so you can use plaintext passwords but they will be sent encrypted.
Besides those I think its pretty good setup.

Setup mailscanner and spamassasin in order to get a production one server.