How to Fix the “Cannot Send Mail” Message on iPhone
While the Mail app is convenient for iPhone users and even provides AI features, there are times when it just doesn’t work as expected. If you’re seeing an alert for “Cannot Send Mail” on iPhone when trying to send an email, it’s likely due to one of the following causes.
1. Use Clean Email
When you’re trying to send an email that just won’t go, you don’t always have time to go through troubleshooting steps to resolve the issue. If you’re receiving the “Cannot Send Mail” message on iPhone, consider using a different email app.
Clean Email not only allows you to send, reply, and forward messages, but maintain a clutter-free and organized mailbox for any IMAP account and on any device, including iPhone, iPad, Android, Mac, and any device via the web app.
Here are just a few features you’ll love:
✅ Unsubscriber: Remove yourself from multiple mailing lists at once or temporarily pause subscriptions for a quick cleanup.
✅ Screener: Screen emails from unknown senders before they clutter your inbox. Then, simply Allow or Block future messages from the senders.
✅ Smart Folders: View related emails using premade filters. You’ll find over 30 Smart Folders created for you for things like Newsletters and Magazines, Online Shopping, Travel, Job Search, and more.
2. Confirm Your Internet Connection
Many times, a weak or unstable internet connection can affect both outgoing and incoming emails. You can check your Wi-Fi connection on iPhone a couple of ways:
- Open the Control Center, make sure the Wi-Fi icon is blue (turned on) and long-press it, and then tap the current network to confirm the connection.
- Open the Settings, select Wi-Fi, make sure the Wi-Fi toggle is enabled, and check the current network connection.
3. Review Your Email Settings
Because passwords can expire and configurations can be mistyped, it’s a good idea to review your email settings to make sure that everything is entered and correct.
- Open Settings and select Apps → Mail.
- Choose Mail Accounts and pick the account.
- Do one or more of the following:
- Verify that the email address is correct and that a password is in place.
- If the password field is empty, this could be the problem. Simply re-enter the password.
- Tap Advanced Settings to confirm the configurations for the outgoing server if applicable.
💡 Tip: You don’t have to worry about advanced and sometimes confusing email settings with Clean Email. Simply sign in to connect your IMAP account and you’re set.
4. Check Your Mail and Device Limits
If you’ve reached your email sending limit for the day or your device storage limit, these can cause issues with sending emails.
The sending limits for Apple Mail are:
- 1,000 messages per day
- 1,000 recipients per day
- 500 recipients per message
- 20MB for incoming and outgoing messages (5GB if using Mail Drop)
To check your iPhone storage and how much space the Mail app is using, follow these steps:
- Open Settings and select General.
- Choose iPhone Storage.
- At the top of the subsequent screen, you’ll see the amount of available and used storage space for your device.
- Move down to the list of apps and you’ll see how much space Mail is consuming.
📌 Note: You may have to select Show All to see the Mail app.
💡 Tip: For help with specific mail accounts, look at how to clear iCloud Mail storage, Gmail storage, and Yahoo Mail storage.
5. Turn Off the Protect Mail Activity Setting
With iOS 15, Apple introduced the Protect Mail Activity setting which helps keep your mail activity away from marketers by hiding your IP address and preventing opened message tracking. And while it’s a great privacy feature, it could interfere with your ability to send emails.
To remedy the “Cannot Send Mail” issue, consider disabling the feature:
- Open Settings.
- Select Apps → Mail.
- Choose Privacy Protection in the Messages section.
- Turn off the Protect Mail Activity toggle.
💡 Tip: Did you know that Clean Email can keep you abreast of data breaches? With the Privacy Monitor, you can see if your email address was involved in a security incident.
6. Check for Server Issues
Another problem with sending emails on iPhone can be completely out of your control and in the hands of the mail server. This can be due to downtime for maintenance or a current repair. Luckily, there are a couple of easy ways to check this.
For iCloud Mail, visit the Apple System Status page. If iCloud Mail has a green light, then everything is fine. But if you see a yellow or red light, there’s a problem.
For other services, visit the Downdetector website. Search the name of the service and choose the correct one from the results. You’ll then see if there are current problems, any reported outages, and options to report your own issue.
7. Send Without Attachments
If the email you’re trying to send includes a large attachment, this can be causing the problem. You may see a “Cannot Send Mail on iPhone Mailbox Full” or “Cannot Send Mail Message Rejected by the Server” error.
Try sending a message from the same account without the attachment. If the email goes through, you may need to reduce the size of the attachment to get it to send.
💡 Tip: If you often receive large emails with attachments in addition to sending them, you can filter, sort, group, and organize your mailbox based on how much space emails take up using Clean Email.
8. Adjust or Disable Your VPN
Sometimes a VPN can affect the sending of emails on iPhone. VPNs can route traffic through a different server which can delay sending messages because of interference with the outgoing port or even block the ability to send emails because of the VPN IP address.
📌 To fix the problem, you can adjust your VPN settings such as excluding the Mail app from the connection or connecting to a different server.
Alternatively, you can temporarily disable the VPN and try resending the message.
9. Remove and Re-Add the Email Account
If it’s a particular email account that seems to be the problem and you’ve already reviewed the settings for it, you can try removing and re-adding the account in the Mail app.
- Open Settings and select Apps → Mail.
- Choose Mail Accounts.
- Pick the account and tap Delete Account.
- Confirm with Delete from My iPhone.
- Return to the Mail Accounts list and tap Add Account.
- Select the email account type and follow the prompts to add it to Mail.
10. Restart Mail and iPhone
Many times, a simple restart can fix issues with apps.
📌 To restart Mail, swipe up from the Home screen to display the open apps. Slide the Mail app off the top of the screen and then use the Mail icon to reopen the app.
Other times, restarting your iPhone is the solution. Simply turn your iPhone off and back on again.
💡 Tip: If you’re having trouble with your iPhone, you can use Clean Email on your other devices with seamless syncing. Check out the full-featured web application and desktop app for Mac.
11. Update iOS
When Apple updates iOS it can include fixes and upgrades as well as address security issues. But there are times when having an out-of-date system can cause problems with usage. So, it’s important to keep your iPhone up to date and running the newest version of iOS.
- Open Settings
- Select General.
- Tap Software update.
You’ll then see if there is an iOS update or if you’re running the latest version.
Head to the Outbox
If you do have an unstable or lost internet connection or mistakenly tapped the Undo Send button, emails that aren’t sent end up in the Mail app’s Outbox. Once you resolve the “Cannot Send Mail” problem, you can check the Outbox and try sending the message again.
- Open Mail.
- Go to the main Mailboxes screen.
- Select Outbox.
- Open the email and hit Send to resend it.
📌 Note that if the Outbox is empty, it won’t display in your list.
If all of the above fail to resolve the “Cannot Send Mail” on iPhone issue, consider reinstalling the Mail app, contacting your email service provider, or notifying Apple Support.
