Fastmail is known for its privacy-focused, fast, and secure email service, trusted by professionals and individuals across the world. Despite its efficiency, users occasionally experience glitches or performance issues—especially when accessing Fastmail on iPhone, Android, or desktop devices. Whether it’s a syncing failure, login error, or complete service outage, this article will walk you through how to fix Fastmail not working issues across all major platforms.

1. How to Fix Fastmail Not Working on iPhone

iPhone users often rely on either the native Mail app or the Fastmail iOS app to manage their email. When problems arise, such as failed login attempts, sync delays, or push notification issues, these solutions can help restore smooth operation.

1.1. Recheck Mail App Configuration Settings

If you’re using Apple Mail to access Fastmail, incorrect configuration could be the root cause.

• Navigate to Settings > Mail > Accounts on your iPhone.
• Select your Fastmail account.
• Make sure the incoming and outgoing mail server settings are:
• IMAP Hostname: imap.fastmail.com | Port: 993 | SSL: ON
• SMTP Hostname: smtp.fastmail.com | Port: 465 or 587 | SSL: ON
• Enter your full Fastmail email address and the correct password or app-specific password if 2FA is enabled.

Any mismatch can prevent emails from syncing or sending.

1.2. Update or Reinstall the Fastmail iOS App

The Fastmail app on iPhone should be kept up to date to avoid bugs.

• Go to the App Store and search for Fastmail.
• Tap “Update” if available.
• If the issue persists, uninstall and reinstall the app.

Reinstallation often clears corrupted cache or settings that are causing glitches.

1.3. Enable Background App Refresh and Notifications

Fastmail requires permission to run in the background and deliver timely notifications.

• Go to Settings > General > Background App Refresh, and ensure it’s enabled for Fastmail.
• Under Settings > Notifications > Fastmail, check that notifications are allowed with alerts and banners turned on.

Disabling these settings can lead to delayed or missed emails.

2. How to Fix Fastmail Not Working on Android

Android users may face challenges like syncing errors, login failures, or slow performance in both the Fastmail app and third-party email clients. Here’s how to resolve them.

2.1. Clear Cache and App Data

Old or corrupted cache files often cause app crashes or sluggishness.

• Go to Settings > Apps > Fastmail (or the email app you’re using).
• Tap Storage > Clear Cache and then Clear Data.
• Reopen the app and log back into your account.

This can help refresh app performance without affecting your emails stored on the server.

2.2. Disable Battery Optimization for Fastmail

Android’s aggressive battery-saving features can block background sync.

• Go to Settings > Battery > Battery Optimization.
• Find Fastmail in the list and select “Don’t optimize.”

You should also check that Sync is enabled globally on your device and for the Fastmail account specifically.

2.3. Update or Reconfigure the Email App

Using outdated apps or incorrect settings can stop Fastmail from functioning.

• Update your Fastmail or email client app via the Google Play Store.
• Recheck IMAP/SMTP settings:
• IMAP Server: imap.fastmail.com, Port: 993, SSL: ON
• SMTP Server: smtp.fastmail.com, Port: 465 or 587, SSL: ON
• If the app continues to fail, remove the Fastmail account from the app and re-add it.

This resets your account’s sync capabilities and clears old settings that may cause issues.

3. How to Fix Fastmail Not Working on Desktop Devices

Fastmail is compatible with major desktop email clients like Outlook, Thunderbird, and Apple Mail. However, issues like authentication failures, sending errors, or syncing delays are not uncommon. Here’s how to fix them.

3.1. Ensure Correct IMAP and SMTP Configuration

A common cause of issues is misconfigured server details.

• Incoming Mail (IMAP):
• Server: imap.fastmail.com
• Port: 993
• Encryption: SSL/TLS
• Outgoing Mail (SMTP):
• Server: smtp.fastmail.com
• Port: 465 (SSL) or 587 (STARTTLS)
• Authentication required

Make sure you’re using your full Fastmail email address as your username.

3.2. Generate and Use App-Specific Passwords

If two-factor authentication (2FA) is enabled, your normal password may not work in email clients.

• Log into Fastmail using a browser.
• Navigate to Settings > Password & Security > App Passwords.
• Generate a new password for your email client.
• Use this new password instead of your primary one in the email client.

This is more secure and bypasses potential login blocks caused by 2FA.

3.3. Check for Conflicts with Firewalls and Antivirus

Overprotective antivirus software or firewalls can block essential Fastmail ports.

• Temporarily disable your antivirus and firewall.
• Try sending or receiving an email.
• If it works, add Fastmail or your email client to the allowed/exception list in your security software.

Don’t forget to re-enable your antivirus protection once you’ve finished testing.

Conclusion

Experiencing technical problems with Fastmail can be frustrating, especially when it interrupts your daily communications. However, by learning how to fix Fastmail not working across iPhone, Android, and desktop devices, you can quickly resolve most common issues. Whether it’s adjusting your server settings, updating your app, or tweaking device configurations, these platform-specific solutions can restore your email functionality with minimal effort.

Remember to always start with the basics—update the app, check your internet connection, and verify your login credentials. If all else fails, Fastmail offers a responsive customer support team that can assist with account-specific problems. By following the steps outlined in this guide, you can ensure your Fastmail experience remains smooth, reliable, and secure across all your devices.