Recently I switched from Googles Workspaces to Fastmail as my mail provider. Not only am I paying less, I'm getting more in return. I love the +notation alternative and that any, not-specified, email address gets dropped into my inbox. No more setting up info@mydomain.com, it just gets delivered to me. Setting all those DNS records is a bit time consuming, error prone and just annoying. So, scripting to the rescue.

Since I've been enjoying F# immensely the last few months (I'll probably blog some more about that in the future), I figured I'd write an F# script to create these DNS records automatically. And good news, I kept all secret bits out of it so I can share it with you, my dearest reader!

The script can be found in a public Github Gist. I won't go over every detail of the script, but you can see that I create a list of DNS records, serialise them and then post them to Cloudflare.

How do you use the script? Copy the script to a file ending with .fsx. Make sure you have at least dotnet 5 installed. Then execute the following line

dotnet fsi [path-to-script] [domain] [cloudflare-auth-key]

Example: dotnet fsi .\set-fastmail-dns-in-cloudflare.fsx kenbonny.net 00000000000-ABCdef

The cloudflare-auth-key can be found in your Cloudflare Dashboard. They have a nice guide on how to create a token.

Fastmail provided an easy list of all the DNS records that should be set to make everything work.

Keep one thing in mind: the Cloudflare API documentation is not up to date when it comes to creating SRV DNS records. Other DNS records require a general JSON structure:

{
  "type": "CNAME",
  "name": "fm1._domainkey.domain.com",
  "content": "fm1.domain.com.dkim.fmhosted.com",
  "ttl": 1,
  "priority": null,
  "proxied": false
}

An SRV DNS record needs a specific JSON structure:

{
  "type": "SRV",
  "data": {
    "service": "_caldavs",
    "proto": "_tcp",
    "name": "domain.com",
    "priority": 0,
    "weight": 1,
    "port": 443,
    "target": "caldav.fastmail.com"
  }
}

Hopefully this saves somebody some setup headache when configuring Fastmail on Cloudflare. Including me, when I add more domains to my account. 😁