Your email was refused from our mail server with one of this errors:

550 5.7.1 Rejecting due to security policy, Please see: ...

Your email has been rejected due to an unspecified reason.

550 5.7.1 Rejecting due to security policy - DNSBL, Please see: ... and ...

Your email server has been put on a list of servers that spam by one or more of the following entities;

• njabl.org
• ordb.org
• dsbl.org
• spamcop.net
• spamhaus.org

Please reference these sites to determine how to remove your email server from the list(s).

550 5.7.1 Rejecting due to security policy - Invalid hostname '...'. Please see: ...

Your email server is providing a hostname which does not properly resolve to an ip address.
This problem can be fixed by your Internet Domain Administrator.
Please forward the error message that directed you here, to that person.

550 5.7.1 Rejecting due to security policy - Helo hostname/ip mismatch, Please see: ...

Your email server is providing a hostname which does not properly resolve to the name of the ip address used by your email server.
This problem can be fixed by your Internet Domain Administrator.
Please forward the error message that directed you here, to that person.

550 5.7.1 Rejecting due to security policy - Inline executable attachement, Please see: ...

550 5.7.1 Rejecting due to security policy - Executable attachement, Please see: ...

You sent an email with an attachement with one or more of the following extenentions:

 vbs .shs .pif .scr .cpl .bat .com .reg .bas .inf .vb .vbe .exe

these are the some of the most commonly suspect file types by which viruses are propogated, and are therefore denied entry into this network.
If you need to send a file or files with one or more of the extensions listed here, please ZIP the file and resend it.

550 5.7.1 Rejecting due to security policy - Recipient has been blacklisted, Please see: ...

The recipient to whom your email was addressed is not allowed to receive email.

550 5.7.1 Rejecting due to security policy - Sender '...' has been blacklisted, Please see: ...

Your email address is not allowed to send email to recipents of this network.

550 5.7.1 Rejecting due to security policy - Unable to validate Sender address ..., Please see: ...

Our mail server was unable to validate your email address, as such, your email will not be allowed to enter this network.

451 4.7.1 Temporary failure - Unable to validate Sender address ..., Please see: ...

Our mail server was temporarily unable to validate your email address, as such, your email will not be allowed to enter this network.
Please try again later.

550 5.7.1 Rejecting due to security policy - Helo or Ehlo MTA greeting expected, Please see: ...

Your email server did not properly identify it's self, as such, your email will not be allowed to enter this network.