Fastmail CardDAV sign-in help
If Cloud Contacts shows a Fastmail rejected sign-in or 401 Unauthorized, the app reached Fastmail's CardDAV server but Fastmail did not accept the username, password, app-password scope, or account eligibility.
Use these values first
Fastmail standard setup
Start with Fastmail's standard CardDAV endpoint. Cloud Contacts performs address book discovery from this server.
https://carddav.fastmail.comYour full Fastmail email address, such as [email protected]A Fastmail app-specific password with Contacts/CardDAV accessWhen sign-in is rejected
Check the account before changing contacts.
Use the full Fastmail email address, not only the short mailbox name.
Create a new Fastmail app password and enable Contacts/CardDAV access for it.
Do not use your normal Fastmail account password.
Verify trial accounts by SMS and confirm the account is eligible for CardDAV.
Revoke any password that was pasted into chat, screenshots, logs, or support tickets.
Fallback setup
Try the direct personal contacts path.
Some clients need Fastmail's direct address book path. Replace [email protected] with the Fastmail email address you use to sign in.
https://carddav.fastmail.com/dav/addressbooks/user/[email protected]/Default[email protected]The same Contacts/CardDAV app-specific passwordFastmail sign-in questions
What does 401 Unauthorized mean?+
Cloud Contacts reached Fastmail, but Fastmail rejected the sign-in before address book discovery could continue. The usual causes are the wrong username format, a regular account password, an app password without Contacts access, or account restrictions on a trial account.
Does this mean my contacts were changed?+
No. A 401 happens before Cloud Contacts can list or import Fastmail contacts, so no Fastmail contact data is synchronized from that failed attempt.
Why does Fastmail mention IMAP, POP, or SMTP in login logs?+
Fastmail's login log explains several protocol types together. For Cloud Contacts, the relevant endpoint is CardDAV. A failed CardDAV or DAV entry around the same time confirms the server received and rejected the attempt.
Open Cloud Contacts and reconnect Fastmail
After creating a new Fastmail Contacts app password, add Fastmail again from Contact Providers.
