Bounce back messages
If you try to send an email and you get a message back to indicate that it could not be sent, you may find that either your domain name or the destination domain name is blacklisted.
Blacklist checkers independently identify spam sources on the internet. These are servers where bulk (meaning hundreds or thousands of) unsolicited mails are sent from. Usually from a hacker or someone that is manipulating an account on the server. It does not necessarily mean that the spam has originated from your account.
The black list records where a server has been independently identified as a spam mail source. Somewhere in the mail path between the sender and recipient a process is checking that the mail has come from or is going to a spam source. The message you get back is often cryptic. One of the first things to do is check whether the problem is at your end, not necessarily your domain, but the server your domain is running from. You can do that using a Black List Check.
If your domain name is ok, check the domain name of the person you are trying to send to.
Black List Check
I came across a useful tool for checking to see if your domain is listed on a blacklist. You can go to here to check:
http://www.inmotionhosting.com/support/tools/blacklist-check
If you find your domain name is listed on a blacklist please bring it to my attention by going to contact us