DB LabsDB Labs

Updated April 7, 2026

Apps

iPhone Mail App Taking Too Much Storage

The Mail app quietly grows as it caches messages and attachments. Here is how to reduce its footprint without deleting anything important.

By Jack Smith  ·  April 7, 2026  ·  7 min read

Quick Fix

The iPhone Mail app stores every downloaded email and attachment locally. Over time this can reach several GB. The fastest fixes are: remove and re-add your mail account (deletes the local cache but keeps your server mail), reduce Mail Days to Sync in account settings to 1 Week or 1 Month, and delete old attachments from your inbox. This typically reduces Mail storage by 60-80 percent without losing any actual email.

Why Mail Grows Over Time

Every time you open an email with an attachment, iPhone downloads and caches the attachment locally so it loads instantly next time. Every IMAP or Exchange message you read also gets cached. Over years this builds up.

Most mail providers let you set how far back to sync. By default, Mail syncs all available mail with no limit. For a business user with 10 years of email and many attachments, the local cache can exceed 5 GB.

Check Mail's Actual Storage Use

Go to Settings > General > iPhone Storage. Wait for the list to fully load. Find Mail in the list (sorted by size). Tap it. You will see a detailed breakdown including App Size and Documents and Data. Documents and Data is the cache.

Fix 1: Limit Mail Days to Sync

This is the cleanest fix. Go to Settings > Mail > Accounts > tap your account > Mail Days to Sync. Change from No Limit to 1 Month or 1 Week. iOS will discard anything older than that from the local cache.

Important: this only affects what is on your iPhone. Mail older than the sync window is still safe on the server, visible in any other mail client, and will load if you scroll back far enough.

Fix 2: Remove and Re-add the Account

This is the nuclear option that always works. Settings > Mail > Accounts > tap the account > Delete Account. Restart your iPhone. Add the account back. The cache will be empty and rebuild only recent mail.

Again, your mail is safe on the server. This only affects what is stored locally on the iPhone.

Fix 3: Delete Large Attachments in Inbox

Open Mail and use the search bar. Search for common attachment terms like PDF or photo or video. Find large old emails with attachments and delete them. You can also sort by size on the web interface of your mail provider for easier identification.

Heads up: Deleting attachments from the iPhone Mail app deletes them from the server too if you are using IMAP or Exchange. Only delete what you truly do not need.

Fix 4: Disable Mail Previews

Previews are small but on very old iPhones they add up. Settings > Mail > Preview > None. This stops the local image cache for message previews.

Fix 5: Use a Different Mail App

If you only use mail occasionally, consider using the webmail interface in Safari instead of the built-in Mail app. No local cache, no storage use. You lose push notifications and offline access but save all the space.

How Much Space You Can Reclaim

Typical results from cleaning Mail storage:

  • Light users: 100-500 MB reclaimed
  • Business users: 1-3 GB reclaimed
  • Users with large attachment histories: 3-8 GB reclaimed

Preventing Mail Bloat

Once you have cleaned it up, keep Mail from growing again by:

  • Setting Mail Days to Sync to 1 Month permanently
  • Not opening mass newsletters with heavy images you do not need
  • Clearing large attachments promptly after using them
  • Running a cleanup once a year as part of your iPhone maintenance

Frequently Asked Questions

Why does my iPhone Mail app use 5 GB of storage?

The Mail app caches every message and attachment you have opened so they load instantly next time. Years of email and attachments add up. Limit Mail Days to Sync in account settings to shrink the cache.

Will deleting the Mail account erase my emails?

No. Deleting and re-adding a mail account only removes the local cache. Your emails are safe on the server and will re-download after you add the account back.

How do I clear Mail cache without losing email?

Change Mail Days to Sync to 1 Month in Settings > Mail > Accounts > your account. This keeps only the most recent mail on the device while everything older stays safe on the server.

Is there a way to see how much space Mail uses?

Yes. Settings > General > iPhone Storage. Find Mail in the list. You will see App Size and Documents and Data separately. Documents and Data is the cache you can reclaim.

You Might Also Like