Yahoo! is getting serious about preventing spam
Yes, Yahoo! is getting so serious about preventing spam that they reject connectoins from EVERYONE! It does not seem to matter who you are or where you are sending mail from, they immediately reject your connection. Here is a sample connection attempt:
421 Message from (18.104.22.168) temporarily deferred - 4.16.50. Please refer to http://help.yahoo.com/help/us/mail/defer/defer-06.html
Connection to host lost.
This technique is called gray listing. It is supposed to reduce spam by always rejecting you the first time on the assumption that a spammer won't call back, but a legimate mail server will. And Yahoo's own bunch of yahoos that answer their support questions seem fond of the automated "gee it must be your fault" messages.
I had not really noticed, but several customers and friends have commented to me that they have problems sending to Yahoo! And if they are eventually successful, their mail goes in the Junk Mail folder. I have noticed that myself. Messages I have sent to Yahoo! users that never in a million years would a content filter have found the message to be spam, yet it ends up in the user's Junk Mail folder. Yahoo! claims that if you implement their Domain Keys technology, then this will reduce the amount mail that gets flagged as spam. Right.
Doing some research today, I found this article and had to laugh a couple of times. If it were not so infuriating then the whole situation would be funny.