Over the last several months, we have had individuals who have been having problems with sending email to Yahoo email addresses.
Yahoo had made a change to their services by "Greylisting" all email servers.
What is Greylisting?
This is a method in an attempt to combat SPAM. What happen is that each time a given mailbox (Yahoo email account) receives an email from an unknown contact (ip), that mail is rejected with a "try again later"-message (this happens at the mail server and is transparent to the end user).
This, in the short run, means that all mail gets delayed...at least until the email server tries to send the email again. The idea here is that spamming software will not attempt to re-send email but legitimate email servers will.
Fixing The Problem...
During this period, we have been doing extensive research on this issue and have attempted to work the issue out according to Yahoo's polices. Going through Yahoo's "recommendations" worked for a short period but then the issue resurfaced.
This is a widespread problem that not only exists for email services provided by Citadelnetworks but by many other ISPs as well.
We will continue to work with Yahoo on ensuring emails are properly delivered to Yahoo users.
Click on the link below for a more in-depth understanding on the changes Yahoo has made that has created this widespread problem.