Mac Mail not receiving emails? Here's how to fix it (account, SSL, and server-side)

When you open the Mac Mail app and new messages never arrive — or you see an offline icon next to a mailbox, or just one account stops working — the problem rarely has a single obvious cause. These issues span multiple layers: your network, your account credentials, server settings, local data corruption, or even an outage on the mail provider's end. Blindly restarting your Mac often doesn't fix it.

This guide breaks down the causes into five categories — network, account authentication, SSL/port settings, mailbox capacity, and server-side issues — and walks you through fixes in the order most likely to work. It covers iCloud Mail, Gmail, Outlook (Microsoft 365), and any IMAP or POP account.

Identify the symptom first

All accounts or just one?

The first thing to establish is whether every account has stopped receiving mail or just one specific account. This narrows down the cause immediately.

All accounts not receiving: likely a network issue, a Mail app crash, or a macOS-level problem
One account not receiving: the issue is specific to that account — credentials, server settings, mailbox capacity, or a provider outage
Can send but not receive: the incoming server (IMAP/POP) is the problem. Sending uses a separate SMTP path, so it's a useful signal when it still works

Click the status indicator in the top-left of the Mail window (the spinning rainbow gear or warning triangle) to see which accounts are reporting errors.

Read the error icon and message

In the left sidebar, a warning icon (triangle or lightning bolt) next to a mailbox name means that account is offline. Click it to see the error detail. Here are the common messages and what they mean:

"The server is not responding": Mail can't reach the server — network problem or provider outage
"The username or password is incorrect": authentication failure — usually a changed password or a 2FA-related issue, not an actual typo
"The server does not allow SSL connections": port and SSL setting mismatch
"The mailbox is full": server-side storage limit reached

The error message alone often tells you which section of this guide to jump to.

Check your network and basic app behavior

Wi-Fi or wired connection

Open Safari and try loading a page like https://www.apple.com. A Wi-Fi icon in your menu bar doesn't guarantee internet access — your router may have lost its upstream connection even while your Mac is connected to it locally.

Force-quit and relaunch Mail

Small bugs in the Mail process are fixed by a full restart. Use this sequence:

Click the Apple menu > Force Quit
Select Mail > Force Quit
Wait a few seconds, then reopen Mail

Restart your Mac

Go to the Apple menu > Restart. If macOS updates were waiting to install, they'll apply during the restart — and some Mail connectivity problems are caused by stale system state that a reboot clears.

Account authentication problems

When Mail says "The username or password is incorrect," the actual password is rarely wrong. Something else has changed.

Password changes and two-factor authentication

If you recently changed your password on another device or in a browser, Mail on your Mac may still be using the old one. Go to System Settings > Internet Accounts, select the affected account, and update the password to your current one.

If you've enabled two-factor authentication (2FA) on an account, many services won't accept your regular password for IMAP access — you need a separate app password for each mail client.

Gmail app password setup

Google has phased out plain-password IMAP access. To use Gmail in the Mac Mail app you need one of these:

Add the account via System Settings > Internet Accounts > Google — this uses OAuth and is the recommended approach
Generate an app password (requires 2-Step Verification to be enabled on your Google account)

If your Gmail account was added with a plain password instead of OAuth, remove it and re-add it through the Google entry in Internet Accounts.

iCloud app-specific password

If you have two-factor authentication on your Apple ID (which is now required for most Apple ID features), third-party mail apps need an app-specific password to connect to iCloud Mail. Go to appleid.apple.com > Sign-In and Security > App-Specific Passwords to generate one.

The built-in Mac Mail app connects to iCloud through your Apple ID system account, so this is only needed if you added iCloud Mail manually with server settings rather than through Internet Accounts.

Outlook / Microsoft 365 Modern Auth

For work or school accounts using Exchange Online, IT admins sometimes block plain IMAP access. If you're getting authentication errors with an Outlook or Exchange account, remove it and re-add it via System Settings > Internet Accounts > Microsoft Exchange — this uses Modern Authentication (OAuth) and is more reliable than manual IMAP setup.

Check incoming server settings (IMAP/POP3)

Port numbers and SSL/TLS combinations

If you see "The server does not allow SSL connections," the port number and SSL toggle are mismatched. These are the standard values:

IMAP + SSL/TLS: port 993
IMAP without SSL: port 143 (deprecated by most providers — avoid)
POP3 + SSL/TLS: port 995
POP3 without SSL: port 110

Check your current settings at Mail > Settings > Accounts > [account] > Server Settings. If SSL is on but the port is 143 or 110, the connection will fail.

Re-enter settings via System Settings > Internet Accounts

If the Server Settings tab looks wrong, it's more reliable to fix things from System Settings rather than from within Mail:

Open System Settings > Internet Accounts and select the account
Check the incoming mail server hostname, port, and SSL setting
If you're not sure what the correct values are, look them up on your provider's support site under "IMAP settings"

Standard server settings by provider

These are the incoming server (IMAP) details for common providers:

iCloud Mail: imap.mail.me.com / 993 / SSL
Gmail: imap.gmail.com / 993 / SSL (OAuth recommended)
Outlook.com / Hotmail: outlook.office365.com / 993 / SSL
Yahoo Mail: imap.mail.yahoo.com / 993 / SSL
AOL Mail: imap.aol.com / 993 / SSL
Comcast / Xfinity: imap.comcast.net / 993 / SSL

For any other provider (work email, ISP-provided address, BT Internet, etc.), search your provider's support site for "IMAP settings" — they're the authoritative source.

Check mailbox capacity

When your mailbox on the server reaches its storage limit, the server stops accepting new messages. Senders may receive a bounce with something like "mailbox full." Log into the web version of each service to check your usage:

iCloud: icloud.com > Settings — free tier is 5 GB shared across all iCloud data
Gmail: mail.google.com — storage bar at the bottom of the page; free tier is 15 GB shared with Drive and Photos
Outlook.com: outlook.com > Settings > Storage — free tier is 15 GB

If you're over the limit, delete large emails with attachments or upgrade your storage plan.

Force a fetch and rebuild the mailbox

Get all new messages shortcut

Go to Mailbox > Get All New Mail in the menu bar, or use the keyboard shortcut Cmd+Shift+N. This forces Mail to check all accounts immediately. To fetch from a single account, use Mailbox > Get New Mail In > [Account Name].

Rebuild a mailbox

After extended use, the local index for a mailbox can become corrupted and cause receiving to stall silently.

In Mail, click the affected mailbox in the left sidebar to select it
Go to Mailbox > Rebuild in the menu bar
Wait for it to complete — this can take a few minutes if the mailbox is large

Regenerate the Envelope Index

If rebuilding doesn't help, try regenerating the Envelope Index — the database Mail uses to track messages and search them.

Quit Mail completely (Cmd+Q)
In Finder, go to Go > Go to Folder and enter: ~/Library/Mail/V10/MailData/
Move (don't delete) these files to a temporary folder on your Desktop: Envelope Index, Envelope Index-shm, Envelope Index-wal
Reopen Mail — it will rebuild the index from scratch automatically

Moving rather than deleting means you can restore the originals if something goes wrong.

Suspect a server-side outage

If none of the above has fixed it, the problem may be with the provider's servers, not your Mac. Check the service status pages:

Apple / iCloud Mail: apple.com/support/systemstatus
Google / Gmail: google.com/appsstatus
Microsoft 365: check the Service Health dashboard in the Microsoft 365 admin center (or ask your IT admin)

Searching for "Gmail down" or "iCloud mail outage" on X (formerly Twitter) can also surface user reports before the provider updates their status page.

Last resorts if nothing else works

Remove and re-add the account

If settings have become corrupted somewhere in the account configuration, removing and re-adding is often the cleanest fix.

Go to System Settings > Internet Accounts, select the account, and delete it
Wait a few minutes, then add the account again — use OAuth (the provider-named option) rather than manual IMAP/POP setup when possible

Removing an IMAP account from your Mac does not delete any mail from the server. If you're using POP3 with "remove from server after download" enabled, your only copy of older messages may be local — export them first from File > Export Mailboxes just in case.

Test with a different mail app

Install Thunderbird or another mail client like Spark or Airmail, and try adding the same account there. This tells you:

If the other app receives mail fine: the problem is specific to Mac Mail — try the account removal and re-add above, or consider creating a new macOS user account to rule out a profile-level issue
If the other app also fails: the issue is with the account or the server, not Mac Mail itself — focus on your provider's support

Summary checklist

Here's the full sequence in order of priority:

Check the status indicator — read the error message
Verify network connectivity; force-quit and relaunch Mail
Re-enter your password; generate an app password if 2FA is enabled
Check incoming server hostname, port, and SSL setting
Check mailbox storage capacity on the web
Force-fetch with Cmd+Shift+N; rebuild the mailbox
Move Envelope Index files and let Mail regenerate them
Check your provider's service status page
Remove the account and re-add it via OAuth
Test with a different mail app to isolate the fault

Steps 1–5 resolve the vast majority of cases. Save the rebuild and index regeneration steps for after you've confirmed credentials and server settings are correct — they take more time and are less often the root cause.

Mac Mail not receiving emails? Here’s how to fix it (account, SSL, and server-side)

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