Proton Mail or Fastmail: which is better for a custom domain?

What does each plan cost with your own domain?

Proton Mail Plus costs $29.88 for the first 12 months and $47.88 a year after; Fastmail Individual costs €60 for 12 months. On Proton's pricing page, Mail Plus is $2.49 a month billed for 12 months against a $4.99 list price, and Proton Unlimited is $6.49 a month, billed $77.88 first and $119.88 at renewal.

Fastmail's pricing page lists Individual at €6 a month, €5 a month on a 12-month term, and cheaper per month on 24 and 36 months. Duo is €96 a year for two users and Family is €132 a year for up to six. The currencies differ, and Fastmail's figures include tax, so compare the order of size rather than the cents.

The jump in Proton's renewal price is the thing to remember: the first-year price is not the price of year two.

How many custom domains and addresses do you get?

Proton Mail Plus gives 1 custom domain with 10 addresses, Proton Unlimited gives 3 domains, and Fastmail's pages state no domain count. Proton's page says Unlimited has 15 extra addresses, and both of its plans include a catch-all.

Fastmail's Individual plan says you can use your own domains to make custom addresses, and Duo and Family list custom domains as included. No number is printed on the pricing page, so the limit is not quoted here. Fastmail's Basic business plan does not support custom domains.

If you want two or three separate domain names, such as a personal one and one for a side project, Fastmail's wording points to fewer limits, while Proton's plan table gives a hard count to plan around. The page Proton Mail vs Tuta for a custom domain shows how a third provider counts domains.

How many DNS records does each provider need?

Proton lists eight records; Fastmail's default list has six, with DMARC not covered by the pages read. According to Postelva's survey of 12 November 2026, a Proton domain needs one verification TXT, two MX, one SPF TXT, three DKIM CNAME and one DMARC TXT, which makes 8. Fastmail's default DNS page lists two MX, one SPF TXT and three DKIM CNAME records, which makes 6, plus optional SRV records for automatic client set-up.

Proton's SPF include is _spf.protonmail.ch; Fastmail's is spf.messagingengine.com. A domain may hold only one SPF record, so when you move from one to the other you change the include rather than adding a second record. The values are shown in each provider's own domain screen, and the full lists are in how to set up Proton Mail with a custom domain and how to set up Fastmail with a custom domain.

Postelva has one-click DNS templates for Proton Mail, Fastmail, Zoho Mail, Google Workspace and Microsoft 365, plus an SPF + DMARC template and a "no email" template for a domain that sends nothing, so both providers can be applied in one click.

Can you buy the domain from the provider?

Fastmail registers domains for paid accounts; Proton does not sell any. Fastmail's help page lists .com, .net, .org, .io, .ac and .sh, available once an account is older than 7 days and not on Basic plans. Its page does not publish prices, and says it uses stored payment details to register and renew.

Proton's custom domain help page tells you to buy the domain from a domain registrar. The domain is therefore always a separate purchase on Proton, and it is separate on Fastmail too if you want a different extension, a different payment method or a domain that does not sit inside your mail account.

A domain bought outside the mail account survives the day you leave the mail provider. Postelva sells a .com for $12.49/year, the same price on every renewal, with free, requested from the client area if you transfer it, and the domain stays in your name.

Can you pay with crypto?

Proton accepts Bitcoin as account credit; Fastmail lists no crypto option on the pages we read. Proton's help page says the Bitcoin option works on the Bitcoin network only, with no Lightning, no Monero and no Ethereum-based tokens. You create a free account first, then buy credit. There is no autopay: you renew by hand, and at least 24 hours before the bill falls due. The credit does not expire.

Fastmail's pricing and domain pages mention stored payment details and a free trial but name no crypto method, so we do not claim one. The domain at Postelva is paid in BTC, USDT, USDC, ETH, SOL, LTC, with a $25 minimum top-up and no identity document; the mailbox is paid wherever the provider accepts. Our overview of the field is in the best private email provider with a custom domain.

Which one should you choose?

Choose Proton Mail for one domain with Bitcoin credit, and Fastmail for a household or several domains on one plan. Proton Mail is the cheaper first year on the published prices. Fastmail's per-user plans cover two or six people under one account.

The choice is not permanent. The address lives on the domain, so moving between the two means changing the MX, SPF and DKIM records at the registrar, not telling your contacts anything. Lower the TTL a day before the move and keep the old account until mail from the new one arrives.