Table of Contents

What Does Apple Mail Messages Stuck in Outbox Mean?
Common Causes of Apple Mail Emails Stuck in Outbox
How to Fix Apple Mail Messages Stuck in Outbox
Advanced Troubleshooting
Prevent Email Loss When Messages Won’t Send
How to Prevent Emails from Getting Stuck Again
When the Problem Is Provider-Specific
Author’s Verdict

Apple Mail Messages Stuck in Outbox -Troubleshooting Guide for 2026

Published By Mohit Kumar Jha

Approved By Anuraag Singh

Published On March 17th, 2026

Reading Time 7 Minutes Reading

Apple Mail messages stuck in Outbox are a common issue that prevents emails from being sent on Mac, iPhone, or iPad. It usually happens due to:

Poor internet connectivity
Incorrect SMTP settings
Large attachments
Temporary server problems

As a result, your messages remain unsent and can disrupt important communication. In this guide, you will learn all the reasons behind this Apple Mail emails stuck in Outbox problem and the quickest ways to fix it so your emails are sent normally again.

What Does Apple Mail Messages Stuck in Outbox Mean?

When an email is stuck in the Outbox, it means Apple Mail tried to send it but couldn’t complete the process. As per my research, this usually happens due to:

Incorrect outgoing mail server (SMTP) settings
IMAP authentication failed issues
Poor or unstable internet connection
Large attachments
macOS or iOS glitches
IMAP server timeout

These are the common reasons behind this. Next, I’ll explain how these can create issues and how to resolve them.

Also read: Enable IMAP in Google Workspace

Common Causes of Apple Mail Emails Stuck in Outbox

If your emails keep getting stuck in the Outbox, one of the issues below is usually responsible. Apple Mail relies on these settings to send messages:

Correct outgoing server settings
Stable internet access
Proper authentication

When any of these fail, the app cannot work properly and shows Apple Mail messages stuck in Outbox. Understanding these common causes will help you figure out exactly what’s blocking emails and fix it faster:

#1. Incorrect SMTP Settings

This happens after changing passwords or switching networks. Check these details carefully:

SMTP server address
Port number (usually 587 or 465)
SSL/TLS enabled
Correct username and password

If any of these are wrong, Apple Mail cannot send emails. To ensure data continuity, it is recommended to backup Apple Mail to external hard drive or a local drive. So that you can access your data without the internet, and Mac Mail.

#2. Internet Connectivity Problems

Sometimes the issue isn’t Apple Mail; it’s the network. I know this is a basic thing, but to resolve Apple Mail emails stuck in Outbox, check:

Wi-Fi stability
VPN interference
Firewall restrictions

A weak connection can interrupt sending and cause the message to be stuck in the Outbox. Not only this, but sometimes VPN and firewall also create problems in sending and receiving messages.

So, turn off the VPN and Firewall services (if possible), then open your Mac Mail, and try to send messages from it, and ask your colleagues, or friends, to send any email, and if sending and receiving is okay, without any issues.

Then, the issue is either with your internet, VPN, or Firewall.

#3. Large Attachments

Emails with large files sometimes create issues when sending. For instance:

Attachments over 20-25 MB most of the time get stuck
Some mail providers enforce lower limits

#4. Mail Server Authentication Errors

If your email provider rejects authentication, it leads to Apple Mail messages stuck in Outbox. This can happen when:

Password changed recently
Two-factor authentication enabled
App-specific password required

#5. Outgoing Server Offline or Timeout

Sometimes the mail server itself is down, which creates the issue even when loading emails. You can verify this by:

Checking the provider status page
Sending email from webmail

If Webmail works but Apple Mail doesn’t, the issue is local.

How to Fix Apple Mail Messages Stuck in Outbox

If your messages won’t send, follow the step-by-step fixes below in order, starting with the simplest:

Fix 1. Send the Message Again

Open the Outbox and try:

Double-click the stuck email
Click Send again

If the issue was temporary, this works, and your service will run as before.

Fix 2. Check Outgoing Mail Server Settings

On macOS:

Open Mail > Settings (Preferences)
Go to Accounts
Select your account
Click Server Settings
Verify SMTP details

On iPhone/iPad:

Settings > Mail > Accounts
Select account
Account > SMTP
Check Primary Server

I’ve fixed the issue many times just by correcting the SMTP port or password.

Fix 3. Remove and Re-Add the Email Account

When nothing else worked, this approach will 100% resolve the Apple Mail messages stuck in Outbox issue:

Steps (macOS):

Mail > Settings > Accounts
Select account
Click “–” to remove
Add the account again

This refreshes all server configurations.

Fix 4. Delete the Problem Email

If only one message is stuck:

Move it to Drafts
Recreate the email
Send again

I do this when attachments cause problems.

Fix 5. Check Attachment Size

Try:

Compressing files
Using cloud links (iCloud, Google Drive, etc.)

Large files are an issue; try to reduce the size of the attachments, or back up the attachments, then delete them to resolve the issue.

Fix 6. Disable VPN or Security Software

VPNs and firewalls can block SMTP ports. So, always test by:

Turning off VPN
Sending email again

If it works, adjust network settings.

Fix 7. Restart Apple Mail or Device

I’ve fixed temporary glitches by:

Force quitting Mail
Restarting Mac/iPhone

Advanced Troubleshooting for Apple Mail Messages Stuck in Outbox

If all the fixes we discussed above failed, then try this:

Step 1. Check Mail Activity Window (macOS)

Go to:

Window > Activity

This shows sending errors in real time.

Step 2. Use Connection Doctor

Apple Mail has a built-in diagnostic tool:

Window > Connection Doctor

These steps are useful for identifying authentication or server issues quickly.

Prevent Email Loss When Messages Won’t Send

When emails remain stuck in the Outbox for a long time, there’s always a risk of losing important drafts, attachments, or entire mailbox data, especially if you remove and re-add the account during troubleshooting. In situations like this, I recommend creating a safe backup of your mailbox before making major changes.

For the same reason, SysTools IMAP Downloader is suggested by the MVPs to download and store all your emails locally, including unsent messages, so nothing gets lost even if the account needs to be reset.

For Windows For macOS Purchase Now

It ensures you have a complete copy of your mailbox that can be restored anytime. By securing your data first, you can troubleshoot the Outbox issue with confidence instead of worrying about accidental data loss.

So, download this now for free, and backup your Mac Mail data in preferred file formats, i.e. PST, MBOX, EML, MSG & PDF.

How to Prevent Emails from Getting Stuck Again

Managing multiple mail accounts, these practices help:

Keep SMTP settings updated
Avoid sending large attachments
Maintain a stable internet connection
Use app-specific passwords when required
Update macOS/iOS regularly

When the Problem Is Provider-Specific

Some email services (Gmail, Outlook, Yahoo) require special settings:

For example, Gmail needs:

App password
“Allow less secure apps” is disabled
Correct ports

Author’s Verdict

Whenever Apple Mail messages stuck in Outbox, start with the SMTP settings and connectivity; these solve the problem most of the time. If not, removing and re-adding the account usually fixes configuration issues.

I hope, after following these fixes, you’ll easily resolve the Apple Mail emails stuck in Outbox.