Since then, we've had many issues getting emails accepted for delivery to Xtra/Yahoo. For long periods of time they will defer all emails, then accept a few, and then go back to deferring all emails.

The answer seems to be to wait 4 hours. Which we've done. A lot.

Yup. Get used to it - there's nothing you can do about it, and it's going to go on for somewhere between a few days and several weeks depending on your volume of mail, the phase of the moon, and probably at least one or two other factors...

I've had the same problems in the past with when moving mail servers for even some of the largest companies in the world - despite significant trying at multiple levels, Yahoo seem completely uninterested in doing anything.� SPF and/or DKIM might help, or they might not (there's no real proof either way).

The best option we've found is to gradually move mail over to the new servers overs a period of a several weeks.� You'll still see delays, but the volume of mail impacted by them should be smaller, and that mail should get through faster (due to smaller back-ups).

After somewhere between 1-4 weeks things will start to flow normally.� (Or at least, as "normal" as it gets for mail to Yahoo).

� Scott