did my mail server get listed as spammer?

[Hubie]

Two times today have emails I sent to customers failed and returned to me by a program that blocks spam (one was barracuda which after research google appears to be very scammy, the other was comcast, which seems legit). Both had links to fill out my info my mail servier

Did my mail server rearlly get flagged for spam? How can I really found out for sure?

[willybfriendly]

If you do a search for email blacklists you should find a number of tools that can tell you if you are listed on any of the common RBL's.

[phranque]

do you know the IP address for your SMTP server?
you can do lookups on spamhaus, openrbl, spamcop, ...

[Status_203]

Check the returned emails carefully, including the headers. They may tell you on what basis the email was blocked.

[piatkow]

Bounced from a mailing list or were these person to person messages? Dedicated server or shared?

At one extreme P2P messages on a dedicated server need serious investigation
For a newsletter on a shared server make a note of the addresses and see if it happens again next time.