Apple Mail Not Sending Emails on Mac? How to Fix It in 2026

When the Mail app on your Mac won't send, the cause is almost always one of four things: the account is offline, the outgoing (SMTP) server is wrong or missing, the provider rejected your sign-in, or something on the network is blocking mail. Click the warning icon next to the account, then run Window > Connection Doctor to see which one it is.

Nothing feels quite as stuck as a reply you were sure had gone out, still sitting in the Outbox an hour later. This guide goes in the order I check things myself: read what Mail is telling you, fix the outgoing server, sort out sign-in for Gmail, Outlook.com and iCloud, rule out the network and sending limits, and get the urgent message out while you work on it.

Start with what Mail is telling you

Apple Mail usually says why it can't send. A warning symbol or lightning bolt appears next to the account's inbox in the sidebar, or in the top-right corner of the window, and clicking it shows the status, according to Apple's troubleshooting article. Before anything else, load any website in Safari to confirm the Mac itself is online.

Match what you see to the likely cause:

Run Connection Doctor

Connection Doctor is Apple Mail's built-in test for every account's incoming and outgoing server. Apple's Connection Doctor guide walks through it:

1. In Mail, choose Window > Connection Doctor.
2. Read the status for each account and follow the instructions in the Details column. Double-clicking that text opens the account in Mail's Accounts settings.
3. To watch what Mail does while it tries to connect, click Show Detail, then Check Again.
4. After any change, click Check Again to see whether it worked.

If Apple Support asks you to turn on Log Connection Activity, know that Apple warns the logs can include personal information, including the content of your emails. Turn it off again once you've sent the logs.

Why is my email stuck in the Outbox in Apple Mail?

An email stays in the Apple Mail Outbox when the account is offline or the outgoing server didn't answer. While an account is offline, Mail can't send, but anything you click Send on waits in the Outbox and goes out automatically once the account is back online (Apple).

1. Choose Mailbox > Take All Accounts Online.
2. For a single account, choose Mailbox > Online Status and pick Take [account] Online.
3. Open the Outbox in the sidebar. If the message is still there after a minute, move on to the outgoing server check below.

One setting decides what happens during short outages. Under Mail > Settings > General, Automatically try sending later if outgoing server is unavailable keeps messages in the Outbox and retries them later. With it unchecked, Mail instead shows you other available servers to send through (Apple). I keep it on: a message that goes out five minutes late beats an error box I might dismiss without reading.

The Outbox is also the first place I look when someone says they never got my email. More than once the answer was sitting right there, with a little warning next to it, because I'd closed the laptop on a train before it finished sending.

How to check the outgoing (SMTP) server in Apple Mail

Every Apple Mail account needs an outgoing server, and if it's missing or wrong, nothing sends from that address. Apple's advice in its sending guide is to make sure the server matches what your email provider specifies. You find it in Server Settings:

1. Choose Mail > Settings (called Preferences on older versions of macOS) and click Accounts.
2. Select the account that won't send, then click Server Settings.
3. Under the outgoing mail server, check the Account menu. If it says None, or a server you don't recognize, open the menu and choose Edit SMTP Server List.
4. Check the Host Name, User Name and Password against your provider's settings, then click OK.
5. Click Save, and send yourself a test email.

Leave Automatically manage connection settings selected unless your provider tells you otherwise. With it on, Mail picks the port and sign-in method itself; Apple says to turn it off only as your provider directs (Apple). The same page warns not to remove a server an account is using unless you're ready to choose or add another right away.

Avoid Allow insecure authentication, under Advanced, unless your provider truly offers nothing else. It sends your user name and password unencrypted, which Apple describes in the outgoing server settings.

Outgoing server settings for iCloud Mail

If you set up iCloud Mail by signing in with your Apple Account, Mail fills these in for you. If you added it by hand, Apple's iCloud Mail server settings list the outgoing server as smtp.mail.me.com, port 587, with SSL required (try TLS or STARTTLS if you get an error) and authentication on. The user name is your full iCloud address, and the password is an app-specific password, not your Apple Account password.

Outgoing settings for Gmail and Outlook.com

For Gmail and Outlook.com, skip the manual server entry. Both now expect you to add the account through the provider's own sign-in, which the next section covers.

Why Apple Mail stopped sending from Gmail or Outlook.com

Apple Mail often stops sending from Gmail or Outlook.com because the account was added with a plain user name and password, which both providers have retired for other mail apps. The fix is to remove the account and add it back through the provider's own sign-in.

• Gmail: Google says Gmail no longer supports third-party apps that ask for your username and password, and points you to the Sign in with Google option instead. If sign-in breaks after a password change, Google's advice is to remove the account from the mail app and add it back that way (Google).
• Outlook.com, Hotmail and Live: Microsoft turned off Basic Authentication for every Outlook account on September 16, 2024. Apple Mail uses the newer sign-in automatically when you add the account as Outlook.com; if you see password prompts or connection errors, Microsoft says the account was probably set up the old way, so remove it and add it again as Outlook.com (Microsoft).
• Work email on Microsoft 365 or Google Workspace: your company's IT team manages the account, so check with them before changing server settings.

The time this bit me, I'd changed my Google password on my phone and forgot Mail on my Mac still had the old one. Incoming mail kept arriving for a while, which made it confusing, but every reply sat in the Outbox. Removing the account and choosing Google again fixed it in a couple of minutes.

Why is the Send button grayed out in Apple Mail?

A dimmed Send button in Apple Mail points to the outgoing server for the account you're sending from. Apple's sending troubleshooting page covers the dimmed button and the "can't be sent using the outgoing mail server" message with the same steps: check the outgoing server, run Connection Doctor, and rule out a firewall.

Two quick checks before you go deeper. Look at the From menu in the message window: if you have several accounts, the email may be set to send from one that's disabled or offline. Then check Mail > Settings > Accounts to make sure Enable this account is selected for that address (Apple).

When the network is blocking your email

If Connection Doctor says it can't reach the outgoing server but websites load fine, something between your Mac and the provider is blocking mail traffic. Apple says to check that no firewall is blocking email on port 25, 465 or 587, including firewalls in third-party software, in a router that shares the connection, or run by your provider (Apple).

• Turn off your VPN and try again. Apple specifically names VPNs and other software that interacts with network connections as a cause of "offline" errors (Apple).
• Try another network. Hotel, airport and office Wi-Fi sometimes block outgoing mail ports. Your phone's hotspot is the fastest test.
• Ask your provider. Apple notes that some providers let you send only from certain locations or require stricter settings, such as a name and password for the outgoing server.

I learned the hotspot trick on a coffee-shop network where every message sat in the Outbox and Connection Doctor reported the outgoing server unreachable. Switching to my phone's hotspot sent all of them within seconds, which told me the problem was the Wi-Fi and not my account.

Sending limits and attachment size

Apple Mail can't send a message your provider refuses, and providers cap both how much you send and how big each message can be. Hitting either one looks like a sending failure in Mail.

The iCloud figures come from Apple's iCloud Mail limits. Google says a blocked Gmail account should be able to send again within 1 to 24 hours (Google), and its attachment cap is 25 MB (Google). For work accounts on Microsoft 365 or Google Workspace, the administrator sets the limits.

For a big file, Mail Drop is the Mac's built-in answer. It uploads the attachment to iCloud, where it's kept encrypted for a maximum of 30 days, and it doesn't count against your iCloud storage. With an iCloud account, Mail uses it automatically; with other accounts, Mail asks first (Apple). To switch it on for an account, go to Mail > Settings > Accounts > Account Information and select Send large attachments with Mail Drop. Mail Drop handles up to 5 GB per message and won't take an uncompressed folder, so compress folders first (Apple).

Last resort: remove the account and add it back

When the outgoing server looks right, the network is fine and Connection Doctor still fails, removing the account from Apple Mail and adding it back resets every setting. It's also Apple's final step in its troubleshooting article.

1. If anything important lives only on your Mac, drag it into a mailbox under On My Mac first. Removing an account deletes its messages from the Mac, though copies stay on the mail server.
2. Choose Mail > Settings, click Accounts, select the account and click the Remove button.
3. If other apps use the account, open System Settings > Internet Accounts, select it and turn Mail off.
4. Choose Mail > Add Account, pick your provider from the list rather than Other Mail Account, and sign in.
5. Send yourself a test email.

Those steps come from Apple's account guide. Before you remove anything, Apple also suggests signing in to your provider's website to look for updated terms and conditions, and for iCloud, checking System Settings for notices about your Apple Account (Apple).

How to get an urgent email out while Mail is broken

The quickest way to send while Apple Mail is down is your provider's webmail: icloud.com for iCloud, gmail.com or outlook.com in Safari. Apple suggests signing in to webmail as a test anyway, because it shows whether the account itself works (Apple).

If webmail sends and Mail doesn't, the problem is the Mac's setup. If webmail fails too, it's the account or the provider, so check the provider's status page and stop changing Mail's settings. That one test has saved me from removing perfectly good accounts more than once.

Before you resend from the browser, copy the text of the stuck message, then delete it from the Outbox. Mail sends whatever is waiting there as soon as the account reconnects, so leaving it means the other person gets it twice. For more on sending that hangs in Gmail or Outlook, see why an email says queued; if Mail keeps failing and you're weighing a switch, Gmail vs. Apple Mail sets out the trade-offs.

How to keep Apple Mail sending

• Add accounts by picking your provider from Mail's list, not Other Mail Account, unless your provider isn't listed.
• After changing an email password anywhere, open Mail on your Mac and check for a sign-in prompt the same day.
• Keep Automatically try sending later if outgoing server is unavailable turned on.
• Glance at the Outbox before closing the laptop after sending something important.
• Turn on Send large attachments with Mail Drop for accounts where you send big files.