I know it's probably no comfort, but I've stopped getting them as well. I only get notifications when I log on.
I have no idea, but I asked a computer nerd friend of mine, and here was his reply:
Often, servers will block all mail initiated by the server to addresses outside of the server and domains hosted by it. It is a rather severe restriction, forced by some unprotected mail forms, that could otherwise be found and used by spam distributing bots from the Internet. Allowing spam to be distributed by a mail server could very soon result in blacklisting of the server and significant problems in delivery of legitimate mail to most outside addresses.
To allow arbitrary recipients in mail forms in php, servers will often have a unique php function, for example "h_mail()", that solves the problem. It behaves almost the same way as the standard mail(), but changes the return address from the server to that of the owner of the script that invokes h_mail(), thus making it possible to send mail to arbitrary addresses.
Since his reply sounded as indecipherable to me as some of the memos I received from the Executive while working for the NSW Health Department, I politely thanked him for it, and filed it under "Things To Be Ignored
" (where I usually filed most Health Department memos).