Anyway, if you’re still experiencing Yahoo problems, here’s a quote from the sherpa article that might help:

“From what we have noticed, [the delivery slowdown] really depends on time of day,” says Ted Roberts, Director, Deliverability & ISP Relations, Silverpop. “If you send early in the morning or during a less-busy time, you will not see those problems.”

They go on to suggest avoiding peak hours, like 10am.

I’m not experiencing Yahoo problems myself. This recent campaign sent to my MonkeyWrench list had no Yahoo issues whatsoever, and it was sent at 11am.

But if you’re experiencing issues, you might try segmenting your list for Yahoo recipients…

In MailChimp, when you select a list to send your campaign to, you can specify a segment to send only to Yahoo recipients like this:

Then you might schedule that campaign to go out at 3am to avoid those peak hours.

After that, replicate the same campaign, and send it to another segment of non-Yahoo recipients:

Segmentation may help you with some of your delivery issues to Yahoo, while we’re all waiting for them to fix whatever server issues they’re having.

Learn more about MailChimp’s List Segmentation feature

Update:
Yahoo! has posted an acknowledgment of the situation on their own blog.