If your emails are not being received, there can be any number of reasons. One of the weirdest ones though is that your ISP has coded your email address as a spam address and blocks any emails you send to anyone else who uses the same ISP. You can find out if this is happening by having the recipient who seems not to be getting your emails to check their spam folder. If this happens to you, call your ISP and have the issue escalated to Tier 3. Not many customers make it to Tier 3, but that's what needs to happen to have your ISP make the requisite change on the server. This is not a made up thing. It actually happened just today to one of our most prized, devoted, skilled, intelligent, insightful, kind, caring, sensitive, intuitive, creative, athletic, and incredibly handsome, and highest ranking officials.