Error messages haunt you when you try to send mail with Fastmail in your favorite email app? To send mail using a Fastmail account from an email program, you need the correct server settings, username, and password. Find here the exact Fastmail SMTP server settings to use (or copy and paste).
First, Snake’s Ear
A snake’s ear is entirely inside its head, invisible and remarkably useful.
The massive jawbone functions as part of the auditory setup, for instance. It picks up vibrations from the ground and transmits them directly to the ear. This lets snakes pick up low sounds, too, and makes them sensitive to movement.
What is it I hear you say? You are here not to transmit sound but emails?
Let’s take a peek, as it were, at email’s proverbial jawbone then, and set up Fastmail SMTP for sending:
Copy-Paste These Fastmail SMTP Server Settings to Send Email
| Name | Value |
|---|---|
| Fastmail SMTP server | |
| TLS security | yes (if available) |
| SSL security | yes (if TLS is not available) |
| SMTP port (SSL/TLS) | |
| STARTTLS security | yes (if TLS/SSL is not available) |
| SMTP port (STARTTLS) | |
| Username | Your full Fastmail email address (including the domain) |
| Password | A Fastmail application password (you cannot send mail using your regular Fastmail password) |
To synchronize incoming mail and folders, use these Fastmail IMAP settings; for downloading, you can also use the Fastmail POP3 settings.
Sending through Fastmail not working? How to Check the Fastmail Status for Issues
Copy-Paste These Fastmail SMTP Server Settings to Send Email: FAQ
Ports 465 and 587 are blocked; can I still send through Fastmail?
Yes, in many cases you can. If your software or hardware security system (firewall) prevents you from connecting to Fastmail through ports 465 and 585, try the following settings:
| Name | Value |
|---|---|
| SMTP server | |
| SMTP port | |
| SMTP port alternative | 21, 80, or any other open port |
| Require TLS | yes (if available) |
| Require SSL | yes (if TLS is not available) |
| STARTTLS security | no |
| Username | Your full Fastmail email address |
| Password | A Fastmail application password |
My email program will not let me use ‘@’ in the username; what can I do?
If you cannot use the full email address (including the '@' sign) as a username for SMTP, try
- replacing '@' with any of the following:
#=or/.
Example:me=fastmail.fminstead of me@fastmail.fm
(First published August 2020, last updated December 2025)