In my time consulting for senders on deliverability issues, I’ve heard more than a few clients try to explain to me why inactive recipients are never really a problem – until there’s a problem.

Starting July 15th, there is going to be a problem.

A few weeks ago, we observed the start of a sustained – and substantial – influx of bounces from Yahoo indicating that the intended recipient address was no longer active. I work for an e-mail service provider that sends tens of millions of messages each day, of which a significant fraction are aimed at Yahoo’s inbound infrastructure. We couldn’t help but notice the huge jump in volume of inactive bounces.

Today, I think we know a lot more about why this is happening. The Associated Press and Gizmodo published stories today announcing that Yahoo is releasing apparently abandoned Yahoo e-mail addresses and their associated Yahoo IDs back into general availability as a part of wunderkind Yahoo CEO Marissa Mayer’s plan to revitalize Yahoo’s offerings to stem the erosion of market share to Gmail:

Yahoo Inc. plans to release the inactive accounts unless the current owner logs in again before July 15. After that, the identifications will be available to all comers and will be ready to use again in mid-August.

Historically, Yahoo has retired abandoned IDs at a somewhat more leisurely pace. But the longer a recipient used their Yahoo ID, the longer of a grace period of inactivity was extended to recover the ID. It’s not clear whether that grace period has been shortened dramatically, or if Yahoo had become lax in enforcing it’s own published inactivity policy.

The question is moot: as of sometime in August, inactive Yahoo IDs (for some value of the word “inactive”) will be available for registration by new users.

For senders who have been diligent about engagement and list hygiene, this is something of a non-event. However, for senders who have been relying on a fat cushion of inactive recipients to fly under hard bounce and complaint rate radar, there is likely to be some pain.