Migrating Fastmail Accounts

How to migrate between two Fastmail accounts without any downtime when using a custom domain.

Sign Up

Sign up for a new Fastmail account at https://app.fastmail.com/signup/. You can also sign up using the 1Password promotional discount for 25% off.


Email Routing

To ensure no emails are dropped or lost during the migration, I use Cloudflare's Email Routing feature to temporarily forward emails to the new Fastmail account. This can be done with any other provider that can hold or forward emails during the migration.

In Cloudflare, head over to Email Routing and the Routes tab. Add the new Fastmail account as the Destination Address and verify it.

destination address

cloudflare verify email

cloudflare verify

Back in Cloudflare, enable the Catch-all address feature to forward all emails to the new Fastmail account.

catch all

Go to the Settings tab and click on Enable Email Routing.

enable email routing

It will prompt to delete conflicting records to allow adding in Cloudflare's DNS MX records. Delete all and then click Add records and enable.

delete conflicting dns records

email routing is enabled

Send yourself a test email to see if the catch-all address and forwarding to the new Fastmail account works.

test email

cloudflare email routing dashboard

Migrate Emails, Contacts and Calendars

In the old account, create a new app password. This will be used to migrate emails, contacts and calendars into the new account.

app password

In the new account, go to Migrate, then Import.


Select Other (IMAP / CardDAV / CalDAV) and enter the old account's details. Use the app password created earlier.

import from other

Select everything you want to import and then click Do it.

import what

The import will complete once everything has transferred. Fastmail will also send an email notifying you. It took 15 minutes to migrate 60000 emails (~5 gigabytes).

import history

import complete

Migrate Settings

While the import is finishing, go through each setting and copy it from the old account to the new account. Important settings include:

  • Signatures and compose options.
  • Enable two-step verification.
  • Loading remote images.
  • Create new app passwords for email clients.
  • Blocked senders and spam settings.
  • Display options.
  • Filters and rules (export then import).

We will migrate custom domains in the next step.

Migrate custom domains

In the old Fastmail account, the custom domain has to be removed before it can be added into the new account. In most cases, the domain cannot be deleted until it is also removed from:

  1. User management
  2. Team addresses

Note that trial accounts cannot delete addresses and therefore cannot delete domains. Deleting the entire account is the only way to free the domain.

delete account

Once the domain is deleted from the old account, add it to the new account until it prompts to set up DNS records.

new domain

Back in Cloudflare's Email Routing, go to the Settings tab and click Start Disabling.

start disabling

Choose to Unlock and keep DNS records then click Unlock records and continue.

unlock keep dns records

Head over to the DNS page and start updating the records to Fastmail.

  1. Fastmail has 2 MX records, but Cloudflare has 3 records.
  2. Delete the lowest priority MX record (the highest number).
  3. Update the remaining 2 MX records as fast as possible.
  4. The DKIM CNAME records should be already correct.
  5. Update the SPF TXT record.

fastmail dns

Head back to Fastmail and click Check now to finish configuring the domain to send and receive mail.

finished setup

Test the domain and any custom addresses again.

test email

Update Email clients


Under Account Settings, within Default Identity, update the Email Address field.

default identity

Click Edit SMTP server and update the User Name field.

smtp server

Under Server Settings, Update the User Name field. Thunderbird will prompt for a Restart.

server settings

Enter the new app password when prompted.

app password

Try sending an email, and you may also be prompted for the password again.

app password 2


Under Settings, open Manual setup and account options and select Accounts.


Scroll down and update the IMAP User name and Password then click Save at the bottom.


Go back to Settings and select Identities this time. Scroll down and update the SMTP User name and Password then click Save at the bottom.