Each ISP (Internet Service Provider) has different methods to control SPAM. While most company's SPAM Policies are reasonable and easy to work within, there are several companies that are more strict and will block traffic altogether if they identify a company or server that is sending out SPAM.
While our company keeps a wary eye out for individuals that abuse our servers there are times that legitimate messages can be incorrectly identified as SPAM when all the messages from an email address are forwarded ("automatic forwarding"). When this happens our mail server may be blacklisted and any of our customers will not be able to send messages to that company until they remove the block.
Here's a list of the more commonly used 3rd part email providers (ISP's), but please understand that we reserve the right to update this list at any time.
- Comcast.net (Xfinity)
- Century Link