More tightening of the reigns on email has resulted in the inability to send emails with attachments. This wasn’t intentional. I was following various guides and someone had some additional header_checks entries that I felt would help reduce spam. In the middle of all the entries is the following:
/^Content\-Transfer\-Encoding:(.*)base64$/ REJECT (base_64)
This little line keeps all emails with attachments from going out.
In the /etc/postfix/header_checks file is where you put restrictions on incoming and outgoing email. It is meant to keep mail users from getting spam and from forwarding spam emails with malicious content to others in the business or to others on the internet. That line though can be dangerous if you aren’t familiar with email and could cause you unintended grief if you just copy other’s work, like I did.
If you get the error “SMTP Error: [550] 5.7.1 (base_64)” then check the /etc/postfix/header_checks.