Yahoo! Mail/Sys Admin

Justin Wilson wrote:

We've been having trouble sending to * Getting the infamous
421 Message from (x.x.x.x) temporarily deferred - 4.16.50. Please refer to Help for your Yahoo Account.

I've actually had quite a bit of success with Yahoo. They're slow in
replying so you have to know what to ask for.

Ask them to add you to their white-list.

Once the techs respond, they'll send you a long questionnaire about your
mail servers, management practices, and company policies. Fill it out
and mail it back to them.

You'll be put on a two week monitoring period where they'll monitor
e-mails coming from your servers. At the end of the two weeks, they'll
approve you if you are legit.

Just grin and bear it. Include all relevant information in *every*
e-mail you send them. You'll most likely talk to someone new every
time. If you're patient and craft well-worded e-mails, you should be on
their white-list in about three or four weeks.

I did exactly this and so far the yahoo mail servers haven't been too
troublesome. They slow down the connections sometimes, but it usually
goes through after an hour or two.