Proton Mail Storage Full: How to Free Space Without Losing Mail

When Proton Mail says your storage is full, new mail bounces and outgoing messages won't send until you free up space - that's the short version of what to do. The confusing part is how differently Proton splits storage by plan: on Proton Free, Mail and Drive are separate quotas, so a full Drive won't touch your inbox. On every paid plan, Mail, Calendar and Drive draw from one shared pool, so a photo backed up in Drive can be the actual reason your email is stuck.

Either way, the fix is the same three moves: find out where the space went, clear it out in the order that matters, then make sure the space is actually returned rather than just relocated to Trash.

The short answer#

Check your storage usage before you delete anything - it tells you whether the problem is Mail or, on a paid plan, Drive. From there, the order that gets you back under quota fastest is:

• Empty Trash and Spam first. Deleted mail keeps its full size until the folder is actually emptied, not just moved.
• Review Sent, not just Inbox. Every attachment you've sent lives there in full, in addition to the copy in the recipient's mailbox.
• On a paid plan, check Proton Drive too - the combined pool means a synced photo library can be the real culprit.
• Turn on auto-delete for Trash and Spam (paid plans) so this doesn't quietly refill in six months.

Before you start: where Proton storage actually goes#

Proton Mail uses zero-access encryption, but that isn't what fills your account - normal mail habits are. A few mechanics explain almost every full-storage case:

Email storage generally isn't deduplicated across messages, Proton's included: a PDF you've forwarded to ten people, or that's been forwarded back to you ten times, is stored as ten full copies, not one shared file. Multiply that by every newsletter, receipt, and forwarded thread from the last few years and the total adds up faster than the number of emails you think you've kept suggests.

The other surprise is what counts as free plan storage. Proton Free gives you up to 1 GB dedicated to Mail and up to 5 GB for Drive - two separate buckets, so filling one doesn't touch the other. You don't start at those numbers, either: the base allocation is 500 MB for Mail and 2 GB for Drive, and you unlock the higher limits by completing Proton's short account-setup checklist. On Mail Plus, Unlimited, Duo, Family, and Visionary, that separation goes away - Mail, Calendar, and Drive share one combined allowance, so a large Drive backup genuinely reduces what's left for email.

Where the space actually goes#

How to check your current Proton storage usage#

Do this before deleting anything - it tells you whether you're chasing the right target.

Steps: clear space without losing mail you need#

1. 1

   Check what you're actually working with

   Open the storage bar on web, or Account Settings on mobile, before deleting anything. If the number is higher than your Mail habits explain and you're on a paid plan, check Proton Drive - a synced photo library or backed-up folder is counted in the same total.

2. 2

   Start with Sent, not Inbox

   Every attachment you've ever sent lives in Sent at full size, in addition to the copy sitting in the recipient's mailbox. Sort through it for stretches of time when you remember sending videos, PDFs, or zipped files.

3. 3

   Confirm a message's size before you decide

   Open a suspect email, click the three-dot More menu, and choose View message details to see its exact size. This turns a hunch into a decision before you delete something you might want back.

4. 4

   Clear Spam and any newsletter or receipt folders

   Spam accumulates automatically and is rarely worth a second look. Bulk-select and delete it, along with any folder you use for subscriptions and receipts, then move to the step that actually frees the space.

5. 5

   Empty Trash and Spam - the step people skip

   Deleted mail sits in Trash at full size until you empty it. Open the folder, use the ⋯ More menu, choose Delete all, and confirm. On mobile, open Trash, tap ⋯, choose Empty Trash, and confirm. Do the same for Spam - deleting a message only moves it here.

6. 6

   Turn on auto-delete so this doesn't repeat

   On any paid plan, Settings → All settings → Messages and composing → Messages has an Auto-delete unwanted messages toggle. It clears Trash and Spam automatically 30 days after mail lands there, and it's off by default.

The moves above cover most cleanups regardless of device, but where you tap to do them differs by platform - and if you use Proton Mail Bridge with a desktop client, Trash lives in two places that both need clearing.

Platform differences#

What to do when it doesn't work#

A few situations don't resolve with a straightforward delete-and-empty pass:

• You emptied Trash and the number hasn't moved. Usage figures can take a few minutes to refresh. If it's been longer, sign out and back in, or check from a different device before assuming something's wrong.
• You're on a paid plan, Mail looks nearly empty, but the account is still full. Check Drive next - camera backup or a synced folder is a very common cause, especially on Duo and Family plans where several people share one pool.
• You've cleared everything you can find and you're still over. At that point the honest options are permanently deleting attachments you're genuinely unsure about, or accepting that your real usage needs more room than your current plan gives you.

A faster way to keep this from happening again#

Manually hunting for big attachments works, but it's a chore you'll be repeating in six months once new mail piles back up the same way. AI Emaily connects to your Proton Mail account over IMAP and keeps that sorting running in the background: newsletters and receipts get grouped into their own view as they arrive, so you can bulk-clear the low-value clutter before it has years to accumulate, without touching Sent or anything you're actively using.

It doesn't manage your Proton storage quota directly - that's still Proton's to set - but it makes it far less likely you're back here next year with the same warning. Every suggested action needs your approval before anything is deleted or sent; nothing runs unattended unless you turn that on yourself. We build AI Emaily, and it's designed to sit alongside Proton Mail rather than replace it - the assistant handles ongoing triage while Proton keeps handling your mail.