Frank Bulk wrote:
Q> Does Yahoo! use "greylisting" to reject messages?
A> No.
The most commonly understood form of "greylisting" is where an
SMTP server will reject every message the first time it is
attempted, and then accept it if the sending server retries
later. The theory is that spammers won't retry messages, while
legitimate senders will.
Yahoo! does not utilize this method.
http://help.yahoo.com/l/us/yahoo/mail/postmaster/postmaster-05.html
Whatever they call it is immaterial. The end result to our system is
indistinguishable from real greylisting. Perhaps there's a tiny fraction
that aren't ever deferred, but in general I find the majority of our
queue is destined to @yahoo.com addresses.
I think I'll followup on the other posters ideas of:
1) Implementing a separate outbound gateway just for yahoo.com
2) Advising users to switch to gmail.