Allow for SMTP server without credentials

[LostLogic]

Hello!
Thank you so much for maintaining this script!
I'd really love it if we had the option of using an smtp server without credentials. We have a SMTP server that allow for non-credential validated sending within our internal IP's. So a question of adding credentials or not would be a welcome addition when setting up the script for the first time. It's been solved by commenting out some lines, but for future proofing it would have been nice!
Cheers, and again, thank you!