When the Mailbox Runs Out of Space

Time: about half an hour. Repeat: once a year, and whenever your provider warns you.

When a mailbox is full it stops accepting mail, and the notice goes to the person who wrote to you, not to you. From your side nothing happens at all: no error, no warning banner in the moment it matters, just an inbox that has become unusually quiet. That asymmetry is the reason this job is worth doing before the quota is reached rather than after.

Understand who gets told

The sender receives a bounce message saying the recipient's mailbox is over quota, and you receive nothing. Whether they read it, understand it or tell you is entirely up to them, and a system sending an invoice or a password reset will not tell you anything.

Providers do warn you first, usually with a banner and a message once you cross a threshold. Those warnings arrive in the mailbox that is about to stop working, which is exactly where a warning is easiest to skim past. Treat the first one as a deadline rather than a suggestion.

The interruption is not clean either. Mail rejected while you are over quota is not queued for later in most cases: the sender's server retries for a while and then gives up, and the message is gone rather than delayed.

Go after attachments, not messages

Delete files, not correspondence. Ten years of ordinary written mail is small; a single video, a scanned contract or a phone photograph sent to you is larger than thousands of text messages together.

The practical consequence is that hunting through old conversations to delete them one by one is wasted effort. Twenty attachments will free more space than four thousand messages, and finding them takes one search.

The shape of the problem is also different from what it feels like. A mailbox does not fill up because you receive too much mail. It fills up because a few people sent you large files, years apart, and nothing ever removed them.

Count the trash, the junk folder and the drive

Check what your quota actually includes before you start, because the space is rarely just the inbox. Deleted mail sits in the trash and continues to count against you until the trash is emptied, and so does everything in the junk folder.

On several large providers the mailbox does not have its own quota at all: it shares one allowance with cloud storage and photo backups. A Google account, for example, counts Gmail, Drive and Photos against the same free fifteen gigabytes, which is why a mailbox can suddenly be full after a weekend of taking pictures. Look at the storage breakdown page before assuming mail is the problem.

If the breakdown shows that mail is a minor part of the total, stop here. The half hour is better spent in the photo library.

Delete from the largest down

Sort by size and work downwards, because the first twenty results usually settle the whole problem. Gmail takes larger:10M, which can be narrowed with older_than:2y. Outlook takes size:>10mb and can also sort a folder by size directly. Apple Mail and most desktop clients can add a size column and sort on it.

Work through the results in order, and empty the trash when you finish. Until you do, nothing you deleted has been freed, and people repeat the whole exercise a week later because the number never moved.

Two categories are usually safe to clear in bulk: mail you sent yourself with large files attached as a transfer trick, and old automated reports. Both are large, both are duplicates of something that exists elsewhere, and neither will ever be evidence of anything.

Keep the mail that proves things later

Do not delete anything that documents an obligation between you and somebody else. That is a shorter list than it sounds and it is worth knowing by heart.

Receipts and invoices for anything expensive, warranty documents, insurance policies and their renewals, tax correspondence, contracts and their amendments, correspondence with an employer or a landlord, and any message containing terms that were agreed in writing rather than on a form. Also worth keeping: the thread where a company promised you something, because that promise usually exists nowhere else.

The side effect of a heavy clear-out is that this history goes with it, and nobody notices for a year. The moment you find out is a dispute with a shop, an insurer or a tax office, and at that point the mail thread is the only version of events you have. Deleting it does not save you much space either, since text is not what filled the mailbox.

Move old years out instead of deleting them

Export whole years to your own storage and then remove them from the mailbox. That gets the space back without the loss, and it takes about as long as deciding what to delete would have taken.

Every large provider offers an export, and the file it produces can be opened locally or reloaded into a mail program later. The step people skip is verifying it, and an unverified export is not a backup. Open it, find three messages from different years, check one with an attachment. This is worth doing properly rather than as an afterthought, and keeping your own copy of a mailbox is a job with its own rules.

An export is also the right first move before any of the larger changes: emptying an account you are leaving behind, or moving your mail to a different provider, where you want the old years out of the way before the transfer starts.

Weigh the storage against the evening

Compare the price of more storage against what an hour of your time is worth, because for many people the answer is to pay. Additional storage from a mainstream provider costs a modest amount per month, and it is bought in a minute.

Cleaning is worth the time in two cases: when the mailbox is so full of one-off large files that half an hour removes the problem for years, and when the real cost is not the space but the mess. Paying to keep a mailbox nobody can search is buying room for the same problem, and that is a question about how the mail is filed rather than about gigabytes.

There is a third case for cleaning that has nothing to do with space: an account you are preparing to shut down. Space is irrelevant there, and the work is entirely about what leaves with the mailbox when an abandoned account is finally deleted.

Stop the traffic that never needed keeping

Some of what fills a mailbox never needed to be in it. A confirmation link for a file you downloaded once, a code for a discount, a receipt for a free trial: none of these will be searched for again, and all of them arrive with images and attachments. Sending that class of mail to a mailbox that erases itself keeps it out of the count entirely, which is a cheaper fix than deleting it every year.

The checklist

• Look at the storage breakdown first, and check whether mail is even the problem.
• Empty the trash and the junk folder before measuring anything.
• Search by size, largest first, and work down about twenty results.
• Keep receipts, warranties, contracts, tax mail and anything documenting an obligation.
• Export old years to your own storage, verify the file, then remove them from the mailbox.
• Compare the price of extra storage against the hour it would take, and pay if that is cheaper.