Fastmail vs Proton Mail for a Business Inbox, After Moving Twice

I have moved our business email twice in eighteen months, which is two more times than anyone should, and it has given me an unusually direct comparison. Both tools are good. They are optimised for different anxieties, and if you pick based on the wrong anxiety you will end up doing what I did.

We started on Proton Mail because the encryption story is compelling and because I had a vague sense that it was the responsible choice. Six months in, the thing that drove me out was not encryption at all. It was search. Because messages are encrypted at rest, search happens against a local index that your device builds, and on a mailbox of about 40,000 messages that index took most of an afternoon to construct and then had to exist on each device separately. Searching from my phone for something from 2023 frequently returned nothing until the phone had caught up. For an inbox that functions as a business record, that was the wrong trade.

Fastmail’s search is server-side, immediate, and very good — it will find a phrase inside a PDF attachment from four years ago in under a second. In the year since moving, this has changed how I work more than I expected. I stopped filing things. The folder structure I had maintained for a decade turned out to be a workaround for bad search, and once search was good I deleted it and have not missed it once.

What Fastmail gave up, and what I would want anyone to weigh honestly, is that your mail is readable by the provider. Fastmail is clear about this and their policies are reasonable, but it is a different security model, not a lesser implementation of the same one. If your correspondence includes things where that matters — legal, medical, journalistic — this is not a preference, it is a requirement, and search convenience does not compete with it.

Both handle custom domains well and the setup is comparable — DNS records, about twenty minutes, both with a wizard that checks your work. Proton’s is slightly friendlier for someone who has never seen an MX record. Neither is a differentiator.

Where Proton is meaningfully ahead is the bundle. The subscription includes a VPN, a password manager, and drive storage, and for a solo operator that consolidation has genuine value — one bill, one account, one company to trust or not. We were paying $6.99 a month for the individual plan. Buying those pieces separately, as we now do, comes to about $19 across three vendors. That is a real cost of leaving that I did not include in my original decision and should have.

The migration itself, both directions, was the same story: IMAP transfer of the archive worked fine and took about three hours unattended; the painful part was every service that had our old address on file. I counted 61 accounts needing an email change on the first move. That is the actual cost of switching email providers, it has nothing to do with either product, and it is why I would tell someone to spend a genuinely long time on this decision the first time.

The line I would give: choose Proton if the confidentiality of the contents is a requirement you can name, and Fastmail if your mail is primarily a record you need to interrogate. I chose on vibes the first time and on evidence the second, and the second one has held for a year.