Yahoo Mail reduces default free storage to 20gb

As reported here and elsewhere, Yahoo has reduced the amount of free storage for Yahoo Mail users. The prior limit, 1 terabyte, is now reduced to 20 gigabytes. Users with a mailbox containing with more than 20 gigabytes of messages will be unable to send or receive email until they clear space or purchase additional space. This updated limit took effect on August 27, 2025.

There's no need for email senders to panic, though. Allow me to explain how to identify recipients with newly full mailboxes, and what to do about it.

The details are in the SMTP rejections

Some email senders and email marketing automation platforms are denoting an increase of "mailbox full" and "over quota" rejections, due to this change. If you're looking for these when parsing out bounces from recent email sends, look for the following specific rejections:

• 552 2 Requested mail action aborted, mailbox is over quota
• 552 5.2.2 This message could not be delivered because the recipient’s mailbox is full. Please try again later or contact the recipient directly. See https://senders.yahooinc.com/smtp-error-codes#mailbox-full for more information

What should email senders do?

Twenty gigabytes is a lot of storage. It seems as though there's a good chance that any Yahoo Mail account stuffed with that much mail (or more) might be abandoned, or being used an email archive, if that particular Yahoo Mail user is an email geek like you or me. Regardless, a full mailbox suggests that perhaps this isn't the user's actively used day-to-day email account. I think that the chances of reconnecting with subscribers after mail is bounced due to an overly full mailbox is quite slim.

I, personally, would just suppress those addresses from future sends.

Are bounces bad for you?

A question commonly asked by email senders is whether or not you can suffer from reputation damage if a mailbox provider sees a high percentage of 5xx rejections, or bounces, in response to your email sends. The short answer is yes, kind of, but it's a bit hand wavy.

Long ago, back in the days of yore, AOL would actually take notice of elevated rejections -- elevated attempts to send mail to users who don't exist -- and we even included warnings about high bounces in the "Report Card" process when I led deliverability efforts for ExactTarget. (I didn't design this; I inherited it. But I was and am a fan. I wish that other folks would resurrect the idea of sender report cards to proactively warn of elevated bounce or complaint rates.)

Microsoft will actually block senders that they believe to be engaged in "namespace mining," which means making up email addresses to see which ones might exist, assumably with the intent of spamming them. This is not exactly the same thing, but very high bounce rates are one way a mailbox provider can identify this; thus, high bounce rates = you look like a bad guy and can get blocked.

Other mailbox providers don't seem to openly say that elevated bounce rates will result in your mail not landing in the inbox. (Google doesn't make any mention of this in Gmail's sender guidelines, for example.) But, I've run enough mail servers myself over the years to know that a receiver's MTA logs are easily mined to look for bad actors, and people with excessively high rejection rates stick out as potential bad actors.

Thus, that's a big part of why I suggest that you suppress mailbox full rejections, even though there's not a straight line connection between failing to do this and getting blocked as a spammer.

And don't forget engagement!

A properly implemented lifecycle subscription management process would likely prevent you from getting to this point or even having to worry about this. If subscribers aren't engaging for long periods of time, it's already a good idea to suppress them to prevent future deliverability issues. And if you're not doing that now, think of these "mailbox full" rejections as a nudge in the right direction; another indicator that a subscriber isn't engaging. (Because the mailbox is abandoned more so than they're just bored with your messages; but the principle is the same.)

Everything will be OK

I know some folks are concerned about this change. But if you're an email sender, treat this as a new signal, a new piece of feedback you're getting regarding certain Yahoo Mail accounts, and know that this change isn't likely to be cutting you off from highly interested email recipients.

Even if you're an active Yahoo Mail user, I think chances are low that you're going to fill that thing up in average, daily use.