How to Sync Fastmail Calendar with Google Calendar

Your dentist appointment lives on Fastmail. Your meetings live on Google Calendar. Neither one knows the other exists.

So a colleague books you at 3pm, and you were already busy at 3pm. Keeper.sh fixes that by copying events from one calendar onto the other.

What will this actually do?

Your Fastmail events appear on your Google calendar. Move one on Fastmail and the copy moves with it. Delete it and the copy goes too.

That is a connection, and it runs in one direction only. Fastmail sending to Google does not mean Google sends back.

Want it both ways? Set up a second connection pointing the other way.

Why won't Fastmail take your normal password?

Fastmail refuses to let outside apps sign in with your account password. That one password reaches your mail, your files, your contacts and your billing.

Instead you generate a separate password just for Keeper.sh. You can delete it on its own later, and your account password keeps working.

Open Fastmail's app password settings.
Click Manage app password and access.
Click New app password. Fastmail may ask you to confirm your account password.
Give it a name you will recognise in six months, like "Keeper.sh".
Under Access, choose Calendars (CalDAV).
Click Generate password and copy what appears.

Step five is worth slowing down for. Calendars (CalDAV) is the narrowest option that still works, so the password reaches your calendars and nothing else. The default also covers mail and contacts, which Keeper.sh has no use for.

Fastmail shows the password once. If you lose it, delete it and generate another.

How do you connect Fastmail?

Two boxes appear:

Fastmail Email Address — the full address you sign in with, domain included
App-Specific Password — the one you just generated

Click Connect. Keeper.sh finds every calendar on the account and brings them all in at once. Your task lists stay behind.

How do you connect Google Calendar?

Return to Import Calendars and choose Connect Google Calendar. Keeper.sh shows what it is about to ask Google for:

See your email address
View a list of your calendars
View events, summaries and details
Add or remove calendar events

Click Connect and finish Google's own permission screen. You sign in to Google directly, so Keeper.sh never sees that password.

Which calendar sends to which?

Connecting an account drops you into a short setup of four screens.

Which calendars would you like to configure? Tick the ones you care about now. Everything was already brought in.
Rename Your Calendars. Fastmail tends to call yours "Calendar" and Google uses your email address. Renaming here changes only what you see inside Keeper.sh.
Where should 'Calendar' send events? Pick the calendars that should receive copies.
Where should 'Calendar' pull events from? The same question in reverse.

For Fastmail into Google you only need screen three. Choose your Google calendar there and the connection exists.

You can change any of this later. Open a calendar from your dashboard and use Send Events to Calendars.

How much of the event crosses over?

Settle this before you trust it with anything private. Open the calendar in your dashboard and find Sync Settings.

Three switches live there: Sync Event Name, Sync Event Description and Sync Event Location.

With Sync Event Name off, the copy is titled after the calendar it came from. Your 3pm arrives on Google as a block called "Personal", not "Therapy".

Turn it on and the real title goes through. The Event Name box also accepts {{event_name}} and {{calendar_name}}, so you can word the placeholder yourself.

Below that, Exclusions can drop all-day events. Both sections are Pro on Keeper.sh and included for everyone on a self-hosted install.

What does not come across?

Time and text, and little else. None of the following reaches the copy:

Guests. The copy has no attendees, so nobody receives an invitation from it.
Meeting links. Google Meet, Teams and Zoom joins are not carried over.
Alerts. Reminders do not travel, so Google applies its own defaults instead.
Colours, attachments and categories. None of these are copied.

What does travel: the title, description, location, start and end, the time zone, whether it repeats, and whether it shows you as busy or free.

Keeper.sh does read the guest list on your own calendars, separately from all this. That powers its pending-invite list and lets you RSVP, and it is never written into a copied event.

How quickly do changes show up?

Keeper.sh reads both calendars every minute, on every plan. That half never slows down.

Writing the change onto the other calendar is the part that differs. Free does that every 30 minutes, Pro every minute.

If you are blocking out evenings so work sees you as busy, 30 minutes is invisible. If people book you through a scheduling link, half an hour is long enough to get double-booked.

How far ahead does it look?

Keeper.sh covers a week back to two years ahead. A one-off booking further out than that is not copied until it drifts into range.

Repeating events get more room. A weekly series that began years ago still has its upcoming occurrences copied.

Why isn't it working?

Connecting Fastmail fails with a short error mentioning 401. Fastmail rejected the password. Either your account password went in instead of the app password, or that app password does not cover calendars.

Keeper.sh says "No calendars found". It reached Fastmail but saw nothing it could use. An app password scoped to Files (WebDAV) or Mail (IMAP/POP/SMTP) does exactly this, so generate a new one set to Calendars (CalDAV).

Events arrive on Google titled after the calendar. That is Sync Event Name switched off. Turn it on under Sync Settings.

Changes you make in Google never reach Fastmail. You built one connection and it points one way. Add a second going back.

An entire calendar stops updating, not just one event. Usually a repeating event with a runaway rule. Keeper.sh will not expand a series past ten thousand occurrences inside its two-year window, and hitting that stops the calendar it belongs to.

What does the free plan cover?

Two calendar accounts and three connections. Fastmail is one account and Google the second, so this pairing uses your account allowance exactly.

Nothing caps the calendars inside an account. Ten Fastmail calendars still count as one.

Three connections covers Fastmail to Google, Google back to Fastmail, and one spare.

Would you rather run it yourself?

Keeper.sh is open source under AGPL-3.0, and self-hosting is a genuine option rather than a cut-down one. Every Pro feature comes with it: one-minute updates, unlimited accounts, unlimited connections, Sync Settings and Exclusions.

It is more work, and you should know how much before starting:

A server, a domain and a certificate
Docker and Docker Compose, alongside Postgres and Redis
Your own Google OAuth client, because Google issues credentials per application. Fastmail needs nothing of the sort — a username and a password is the whole story.
Backups, updates, and being the person who gets paged when it stops at 2am

The README covers a single-container setup and a full Compose file. If that reads like a chore, keeper.sh does the same job and funds the project.