Delivery implications of Yahoo releasing usernames

Yahoo announced a few weeks ago it would be releasing account names back into the general pool. This, understandably, caused a lot of concern among marketers about how this would affect email delivery at Yahoo. I had the opportunity to talk with a Yahoo employee last week, and ask some questions about how this might affect delivery.
Q: How many email addresses are affected?

Yahoo is not providing any numbers for how many usernames are being returned to the “available” pool. However, most of these addresses were never associated with an email account. The Yahoo rep told me that the number of accounts with email addresses was “miniscule.” What’s more, the vast majority of these email addresses have been bouncing for a long time. As of July 15th, all the email addresses going back into the pool are bouncing and will be until someone claims the username and activates the email address.

Q: What bounce message are senders receiving when they try to send mail to affected email addresses?

All addresses returned to the pool will bounce with a message indicating that the mailbox doesn’t exist. And most of these addresses have been bouncing with that message for months or years.

Q: Are any of these addresses going to be turned into spamtraps?

Yahoo won’t discuss any specifics of their spam filtering. However, there is always the chance that abandoned addresses will be reactivated to spam traps at any time after they are abandoned. This is on reason bounce handling is so critical.

Q: Is Yahoo going to make exceptions for senders who are opt-in, but may send mail to someone who picked up a reclaimed address?

No. These are old, abandoned email addresses and Yahoo expects senders to bounce handle their lists.

Q: Will sending mail to these non-existent addresses affect Yahoo! reputation?

Most of these addresses have been inactive for a long time, so senders with good bounce handling polices should not be concerned.

Q: What do you recommend to opt-in senders who don’t want to send mail to the wrong person?

Make use of the Require-Recipient-Valid-Since header.

Q: Anything else we should know?

This is a normal process for most ISPs. Usernames and addresses don’t stick around forever and most ISPs recycle addresses.

Overall, I don’t think there are many changes from my previous advice not to worry too much about this. There aren’t going to be huge delivery implications to the username recycling. But I do have some suggestions for senders.
If you haven’t mailed a Yahoo account in more than 6 months, mail it now to make sure it’s deliverable. Most of these accounts have been long term bouncing, and regular mailers should have already removed the address. But, I know some senders segment to the extent that some accounts don’t get mail for months or years. Mail them now.
Remove Yahoo addresses that bounce with “user unknown” “mailbox unavailable” and “mailbox unknown” messages on the first bounce. We know that Yahoo will be releasing some portion of these addresses back into the available pool. You could keep mailing those users and hope that the address starts working, and it might. But that recipient may not be who you think it is. Yahoo is not known for sending fake or incorrect mailbox unavailable messages, so trust their bounces and remove addresses promptly.
If you use email as a “key” for access to an online account, consider implementing the proposed “Require-recipient-valid-since” header. Require-recipient-valid-since is a new header going through the IETF standardization process. This header lets a sender, say a social networking site sending a password reset notification, tell the receiving ISP when the address was originally collected. The receiving ISP can bounce the mail if the account has been recycled since it was collected. I’ll be talking more about this in another post.