How to Fix Apple Mail Running Slow on macOS After an Update?

admin | Apple Apple Mail how to | 5 minutes read | Modified on: 08-09-2026

Switching to a new OS version often provides many new features, performance boost and increased safety. Unfortunately, it happens quite often that users have performance issues with some key apps after the update. The most common issue after the update is the poor performance of the Apple Mail application that can either freeze upon starting or hang up on the process of indexing emails.

When you encounter delays upon starting the Apple Mail app, slow typing of emails, poor loading of emails and constant spinning of the beach ball of death, you are not the only one experiencing these problems.

Now let us examine in detail why this problem appears after an OS update and what steps you can take to solve it.

Why Does Apple Mail Slow Down After a macOS Update?

While installing a new macOS update, a lot of modifications occur in the operating system. Apple Mail is tightly integrated into the system, which means that any modifications at the system level will affect its database and cache.

  • Overhead for Re-Indexing Database: Due to the update, macOS may need to re-index the whole database (Envelop Index files) in order to make it compatible with the new search architecture. If you have thousands of gigabytes of old emails, this process will take a lot of CPU and RAM power.
  • Corruption of Cache Files: In case if your cached files do not meet the requirements of the new macOS build, you will experience application conflicts, problems with the rendering, and memory leaks.
  • Overload by Attachment Caches: The accumulation of attachment caches will overload the application trying to synchronize or organize local directories under new system permissions.
  • Third-Party Mail Plugins Outdated: The Mail plugins built for the previous version of macOS can cause background crashes and UI lags.
  • Problems with IMAP / Exchange Synchronization: System updates may reset network configuration options, and thus, Apple Mail will try to reconnect infinitely or freeze while synchronizing IMAP emails.

Step-by-Step Fixes for Apple Mail Performance Issues

Use these practical solutions to overcome Apple Mail performance problems after an OS upgrade.

Solution 1: Force Rebuild Mailbox Index

When Apple Mail freezes while searching through emails, takes forever to load folders, or doesn’t show the content of the emails, then the fix will be rebuilding the mailbox index.

  1. Open the Apple Mail program.
  2. Select the slow mailbox folder (Inbox/All Mail).
  3. Open Mailbox and click Rebuild.
  4. Done the same thing to the other mailboxes that have many emails.

Note: This process is done in the background and may take anywhere from a few minutes to one hour.

Step 2: Manually Re-Index Apple Mail (Envelope Index Reset)

If “Rebuild” does not help in making the application faster, you may have corrupted database files of your Mail application. “Resetting the Envelope Index” is a process that helps Apple Mail rebuild the entire database without deleting any email.

Step 1. Ensure Apple Mail is completely closed. Press Command (⌘) + Q while inside the app to quit.

Step 2. Open Finder, click Go in the top menu bar, hold down the Option (⌥) key, and click Library when it appears.

Step 3. Navigate to the following folder path:

Containers > com.apple.mail > Data > Library > Mail > V10 (The “V” number may be V8, V9, V10, or higher depending on your macOS version).

Step 4. Open the MailData folder and locate all files starting with Envelope Index (e.g., Envelope Index, Envelope Index-shm, Envelope Index-wal). Move these files to the Trash.

Step 4. Open Apple Mail. The app will display a message stating that it is “Importing Mailboxes.” Allow the re-indexing process to complete.

Step 3: Disable Outdated Mail Plug-ins & Extensions

Compatibility issues involving third-party plug-ins is one of the most common reasons for beachballing or freeze after update.

  1. Open Apple Mail.
  2. Move to Mail > Settings or Preferences in the Menu bar.
  3. Select General tab.
  4. Find the Manage Plug-ins… button from the bottom.
  5. Turn off all third-party plug-ins, apply and restart the Mail program.

Step 4: Clear Apple Mail Cache & Local Storage

As days go by, Apple Mail builds up a huge cache of previews and log files that take up system memory space.

  1. Close Apple Mail.
  2. Launch Finder and select Go > Go to Folder… (or press Command + Shift + G).
  3. Type in the following path:

      ~/Library/Caches/com.apple.mail

  • Select all items inside this folder and move them to the Trash.
  • Restart your Mac to clear inactive RAM allocations.

Step 5: Remove and Re-add Troublesome Accounts

Should the slow performance be confined to a particular email account such as an Exchange, Gmail, or Yahoo account, deleting and adding back the account removes sync logs and establishes proper connection to the server.

Steps:

  1. Go to System Settings > Internet Accounts (System Preferences).
  2. Select the problematic email account.
  3. Tap Delete Account (or disable Mail toggle).
  4. Reboot your computer.
  5. Go back to Internet Accounts and add your credentials to start sync afresh.

Step 6: Optimize Attachment Downloads & Storage

On the other hand, if Apple Mail is configured to download all attachments for viewing without the internet, then the performance of the system will be poor due to insufficient storage space on the hard drive.

Fixing steps:

  1. Open Apple Mail.
  2. From the menu bar, select Mail > Preferences > Accounts.
  3. Switch to the account that you are currently using and switch to the tab “Account Information”.
  4. Update the setting from “Download Attachments” to Recent or None.

Alternative Migration Solution for Legacy Archives

However, sometimes large mailboxes stored in Apple Mail account can also slow down the Apple Mail application. Thereby, it is always better to backup Apple Mail data files regularly into easily accessible file type and empty the inbox folder that is slowing the email client. And to implement the same, one can use MacMister Apple Mail Converter utility. It is an application that transforms Apple Mail data into 15+ saving options with 100% accuracy and correct metadata properties.  The easy GUI of the app allows all types of users to implement the process with ease. Besides, one can use its free demo and save 25 Apple Mail files for free.

Epilogue

A slow Apple Mail application following an update of your Mac operating system (macOS) is a frequent experience, but one that can be easily remedied. This will include letting your computer finish indexing of data in the background, deleting any corrupted Envelope Index files, clearing your cache, and uninstalling unnecessary plugins.