Not to worry, none of the questions you have asked could possibly be viewed as dumb.
SASL is more secure than x-Before-SMTP because my implementation of the pop-before-smtp logic does is not based on successful authorization, but rather a connection. SASL and Relay-Ctrl both send passwords in plain-text. You are disclosing sensitive password information in unencrypted text every time you POP to your server, this is why I recommend using stunnel + pop3.
SASL requires the user to "Login to the SMTP server." Most E-Mail clients support this option, I believe Microsoft calls it "My server requires me to login to send mail". Personally, I don't know what to thing of mailfront. I don't have any experience with it so I really don't have any grounds to formulate a real opinion of either. What I can say is I don't like sending cleartext or unencrypted passwords period. It depends on your view of security to determine if it is more or less secure. One method (SASL/Relay-CTRL) using plain-text can compromise the user account. x-before-smtp with stunnel will not leak any password information, at a worse case scenario you become a open relay for a specific user for a limited amount of time.
Bill, by the way, upgrade your pop-before-smtp (
http://www.stickit.nu/pop-before-smtp), I just released a new version today.
Nathan