Fastmail IMAP SMTP Configuration Guide

Complete step-by-step guide to configure Fastmail IMAP and SMTP settings for any email client including Outlook, Thunderbird, and Apple Mail

Quick Fastmail Settings

IMAP Settings (Incoming Mail)

Server:imap.fastmail.com

Port:993

Security:SSL/TLS

SMTP Settings (Outgoing Mail)

Server:smtp.fastmail.com

Port:587 or 465

Security:STARTTLS or SSL

Before You Start

App Password Recommended

Fastmail supports both regular passwords and app passwords. App passwords are recommended for better security.

Ensure you have an active Fastmail account
Know your complete Fastmail email address and password
Have your email client ready for configuration
Consider enabling two-factor authentication for security

Step 1: Generate App Password (Recommended)

Sign in to your Fastmail account
Click on "Settings" in the top right corner
Go to "Privacy & Security" → "App Passwords"
Click "New App Password"
Enter a name for the password (e.g., "Email Client" or "Outlook")
Select the appropriate permissions (usually "Mail" is sufficient)
Click "Generate password"
Copy the generated password and store it securely

Alternative

You can also use your regular Fastmail password, but app passwords provide better security and control.

Step 2: Configure Your Email Client

Microsoft Outlook Configuration

Open Outlook and go to File → Add Account
Choose "Manual setup or additional server types"
Select "POP or IMAP"
Enter your account information:
- Your Name: [Your full name]
- Email Address: [your-email@fastmail.com]
- Account Type: IMAP
- Incoming mail server: imap.fastmail.com
- Outgoing mail server: smtp.fastmail.com
- User Name: [your complete Fastmail address]
- Password: [Your app password or regular password]
Click "More Settings" → "Advanced" tab
Set incoming server port to 993 with SSL encryption
Set outgoing server port to 587 with STARTTLS encryption
Check "My outgoing server requires authentication"

Mozilla Thunderbird Configuration

Open Thunderbird and go to File → New → Existing Mail Account
Enter your name, Fastmail address, and password (app password if created)
Click "Configure manually" if auto-detection doesn't work
Set the following settings:
- Incoming: IMAP, imap.fastmail.com, Port 993, SSL/TLS
- Outgoing: SMTP, smtp.fastmail.com, Port 587, STARTTLS
- Username: your complete Fastmail address
- Authentication: Normal password
Click "Re-test" and then "Create Account"

Apple Mail Configuration

Open Mail app and go to Mail → Preferences → Accounts
Click the "+" button to add a new account
Select "Other Mail Account"
Enter your name, Fastmail address, and password
Configure manually if needed:
- Incoming Mail Server: imap.fastmail.com
- Outgoing Mail Server: smtp.fastmail.com
- Use SSL for both incoming and outgoing
- Incoming port: 993, Outgoing port: 587
Click "Sign In" to complete the setup

Generic Email Client Configuration

Manual Configuration Settings:

Incoming Mail (IMAP)

Server: imap.fastmail.com
Port: 993
Security: SSL/TLS
Authentication: Normal password

Outgoing Mail (SMTP)

Server: smtp.fastmail.com
Port: 587 (STARTTLS) or 465 (SSL)
Security: STARTTLS or SSL/TLS
Authentication: Required

Custom Domain Email Configuration

Custom Domain Users

If you're using Fastmail with your own domain, use the same server settings but with your custom email address.

For custom domain emails (e.g., yourname@yourdomain.com hosted on Fastmail):

Use the same IMAP/SMTP server settings (imap.fastmail.com and smtp.fastmail.com)
Enter your complete custom domain email address as the username
Use your Fastmail password or app password
All port and security settings remain the same

Alternative Port Settings

If Standard Ports Don't Work

SMTP Alternative Settings

Port 465 with SSL/TLS encryption
Port 25 (usually blocked by ISPs)

POP3 Settings (Alternative to IMAP)

Server: pop.fastmail.com
Port: 995 with SSL/TLS
Port 110 (non-secure)

Mobile Device Configuration

iPhone/iPad Setup

Go to Settings → Mail → Accounts
Tap "Add Account" → "Other"
Tap "Add Mail Account"
Enter your Fastmail email details
Use the IMAP/SMTP settings above
Enable SSL for both incoming and outgoing

Android Setup

Open Email app or Gmail
Tap "Add Account" → "Other"
Choose "Personal (IMAP)"
Enter your Fastmail email and password
Configure with the settings above
Enable SSL/TLS encryption

Troubleshooting Common Issues

Authentication Failed Error

Verify your complete Fastmail email address and password
Try using an app password instead of your regular password
Check if two-factor authentication is affecting login
Ensure IMAP access is enabled in Fastmail settings

Connection Issues

Check your internet connection and firewall settings
Verify the server names and ports are correct
Try alternative SMTP port 465 with SSL
Contact your ISP if they block email ports

Emails Not Syncing

Check your IMAP folder subscriptions
Verify sync settings in your email client
Try refreshing or restarting your email client
Check Fastmail storage quota

Security Best Practices

Use app passwords instead of your main Fastmail password
Enable two-factor authentication for additional security
Always use SSL/TLS encryption for email connections
Keep your email client software updated
Regularly review and manage app passwords

Frequently Asked Questions

Do I need an app password for Fastmail?

App passwords are recommended but not required. They provide better security and allow you to revoke access to specific applications.

Can I use Fastmail with my custom domain?

Yes, Fastmail supports custom domains. Use the same server settings but with your custom domain email address.

What's the difference between IMAP and POP3?

IMAP syncs emails across all devices and keeps them on the server, while POP3 downloads emails to one device. IMAP is recommended for most users.

Does Fastmail support push email?

Yes, Fastmail supports push email through IMAP IDLE, which provides near-instant email delivery to your devices.