How to Make Apple Mail Download All Messages for Offline

Open Apple Mail on a plane, click a message from three months ago, and you see a loading indicator instead of the message — because there is no connection to fetch the body on demand. Search for a subject line you sent last spring and results come back empty, even though you remember writing it. Both symptoms trace to the same default: Apple Mail keeps only recent message headers locally and downloads bodies and attachments from the server when you open them.

That default makes sense for storage. A Gmail account with ten years of archives and embedded images can occupy tens of gigabytes on disk. What it does not account for is the reader sitting on a cross-country flight or working from a hotel lobby with intermittent Wi-Fi who needs access to mail from last quarter.

Changing how Apple Mail handles offline downloads requires two setting fields, applied per account. This guide covers the exact steps for macOS Ventura and Sonoma, the storage cost to weigh before you change anything, how the setting behaves differently on IMAP versus Exchange accounts, and what to check if messages are still not loading after the settings are applied.

Before you start: check storage and your macOS version#

Apple Mail stores offline copies in ~/Library/Mail. A professional account with several years of history and regular file attachments can occupy 15 to 40 GB after a full sync. Before changing the setting, confirm available disk space: open the Apple menu, click About This Mac, then click More Info and Storage. Leave at least 15 to 20 GB free beyond whatever the mail archive is estimated to add.

The settings in this guide are labelled as they appear in macOS Ventura (13) and Sonoma (14). On macOS Monterey (12) and earlier, the same options exist but the Download Attachments dropdown and the Keep Copies label are worded slightly differently in some releases. The steps below note where the label varies.

Both settings apply per account, not globally. If you have Gmail, iCloud, and a work account configured, you apply the change to each one individually. An account left at the default continues to show headers only when offline, so work through every account in the sidebar.

Steps: how to make Apple Mail download all messages for offline#

Work through each account in the Mail sidebar. The two settings that control offline access are both in Mail > Settings > Accounts, under the Account Information tab.

1. 1

   Open Mail Settings

   In the menu bar click Mail, then Settings. The keyboard shortcut is Command-Comma. The Settings window opens with a row of tab icons along the top.

2. 2

   Click the Accounts tab

   Select the Accounts tab — the icon showing an @ symbol in an envelope. Your configured email accounts appear in the left column. Select the first account you want to change.

3. 3

   Click the Account Information tab

   Each account panel has two or three tabs: Account Information, Server Settings, and sometimes Mailbox Behaviors. Click Account Information to reach the offline caching options.

4. 4

   Change Download Attachments to All

   Find the Download Attachments dropdown. The default is typically Recent or None. Change it to All. This instructs Mail to download every attachment body as it syncs — images, PDFs, and any other attachments — rather than waiting until you open a specific message while connected.

5. 5

   Change Keep Copies of Messages for Offline Viewing to All Messages and Their Attachments

   Find the dropdown labelled Keep Copies of Messages for Offline Viewing. On Monterey and earlier it may read Keep Copies of Messages. Change it from its default — often Recent Messages Only or Don't Keep Copies — to All Messages and Their Attachments. This is the setting that determines whether Mail keeps full message bodies and attachment files on disk after the initial download or evicts them to save space.

6. 6

   Repeat for each account in the sidebar

   Click the next account in the left column and repeat steps 3 through 5. Any account left at its default setting stays header-only when offline. Work through every account you need to read without a connection.

7. 7

   Allow the initial sync to finish before going offline

   After applying the settings, Mail begins downloading the full archive in the background. The status bar at the bottom of the Mail window shows a count of messages remaining. Depending on inbox size, account history, and connection speed, the initial sync can take anywhere from several minutes to several hours. Stay connected until it completes.

How the setting behaves across macOS versions and account types#

The two offline settings interact differently depending on the account protocol and macOS version. The table below covers the combinations that affect what offline access looks like in practice.

What to do when messages are still missing offline after changing the settings#

If messages are still showing a loading indicator offline after applying both settings, one of several things is blocking the local cache from being complete.

• The initial sync has not finished yet: check the status bar at the bottom of the Mail window. A count of messages remaining appears during the bulk download phase. Stay connected and let the sync complete before testing offline access.
• The settings reverted after a macOS update or account removal: some macOS point releases reset per-account Mail preferences. Open Mail > Settings > Accounts, select each account, and confirm both settings are still at All. If they reverted, reapply them and let the sync run again.
• Not all folders are included in the local download: Mail may exclude Sent, Trash, and custom folders from syncing unless they are explicitly mapped. Open the Mailbox Behaviors tab for the affected account and confirm the folders you need offline are assigned and not set to store on the server only.
• Disk space ran out mid-sync: if the Mac ran low on storage while downloading, Mail silently stops caching. Free additional space, then go to Mailbox > Synchronize Account to restart the download from where it stopped.
• Spotlight has not finished indexing the local archive: even with bodies cached, search returns incomplete results until Spotlight has indexed ~/Library/Mail. On a large archive this can take several hours after the sync completes. To restart the index, go to Mail > Settings > General and click Rebuild, or select the account in the sidebar and choose Mailbox > Rebuild.
• The account is Exchange under a restrictive policy: if the Download Attachments and Keep Copies dropdowns grey out or revert within minutes of saving, the Exchange or MDM server is overriding the local setting. No Mail preference change will override a server-side policy — the fix must come from the IT administrator.

A faster way to manage email across unreliable connections#

The steps above give Apple Mail a full local archive on the Mac. But client-side IMAP caching is inherently per-device: you configure it on the Mac, then separately on the iPhone, then again after a macOS reinstall or a Migration Assistant transfer. Every new device starts from zero and needs its own initial multi-hour sync.

We build AI Emaily, an AI-native email client that syncs through a server-side layer rather than relying on each device to maintain its own IMAP cache. Because the sync layer sits between your provider and your devices, an offline session on any surface — web, Mac, or iOS — reads from the same cached store. There is no per-device archive to configure and no waiting for an initial bulk sync on a new machine. If recurring offline setup across several accounts and devices is a familiar pattern, the 7-day free trial at aiemaily.com is a practical way to see whether the architecture holds up for your setup.