What is a Whitelist

Many email filters scan the email for certain words or phrases. Email header information is also scanned for misleading information. Some programs incorporate information from email "blacklists," which contain addresses of supposed illegitimate senders or Spammers. This also occurs if you are behind a firewall or if your ISP filters your mail. Unfortunately, legitimate senders can end up on blacklists all too easily now, particularly if their list management provider is incorrectly blackmailed at the server level or ISP level.

Some anti-spam programs use "white lists". For someone using anti-spam software, a white lists is a list of the emails the recipient specifically chooses to accept. Consider including a short line in your emails asking your recipients to add you to their white list.