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Email migration from Proton to Mailbox

How I moved email, calendar and contacts from Proton to Mailbox, on both desktop and mobile.

Simone Silvestroni's avatar

The reason for embarking on such a task has a very short answer. When I chose Proton years ago, I wasn’t bothered by the feeling of being trapped in a walled garden. Now I am.

With Proton I’m not allowed to use any system program such as Calendar and Contacts. Having to go through their own proprietary applications, makes a proper sync quite cumbersome. External email clients are barely supported — on desktop only — and require a daemon running in the background at all times.

A nice plus of the migration is that I’m going to save around €20 per year: money that can be redirected to other digital venues. is hosted in the EU (Germany) on green servers.

The process

The following has been carried out on macOS 10.14.

After getting the gist of how the various services and settings work in my new Mailbox account, I’ve added €3 to become a paying customer. I like this formula, as it leaves me free to fully experiment for a while without committing to an annual payment yet.

I got 50 aliases, including for my custom domains. Setting them up was as easy as adding a bunch of DNS values (TXT and MX) after authenticating the domains with Mailbox. I also improved the spam reputation by setting up SPF, DKIM and DMARC.

Mailbox gave me automatic configuration profiles for macOS’ Mail, Calendar and Contacts applications. While preferring a manual setup for IMAP and SMTP on, I’ve chosen the easy and fast procedure for calDAV and cardDAV.

Next, I’ve exported a full backup of contacts and calendars from Proton. Importing them back on Mailbox was straightforward: all I’ve used was the import functionality from the default Apple applications. To move the entirety of my 25-thousand emails I relied on a manual migration: selecting large chunks of messages at a time (around 1k), using no issue whatsoever.

All in all, despite dreading the idea of wasting time and energy, it was a surprisingly quick job. With zero experience with, it took no more than a couple hours from start to finish.

Side effects

Migrating a whole email system isn’t limited to the above. There’s also the most frustrating consequence of a bad choice: having a gigantic number of accounts registered with an email address tied to Proton. Could be Gmail or a free Outlook or iCloud or whatever: anything that ties me to a system that’s closed in itself and completely outside my control is awfully shortsighted.

I had to alter all my accounts, swapping an address that I’m going to lose soon with one from a personal domain. My domain is under my full control: I can move the hosting, change DNS, nameservers, whatever — it stays with me, while everything else can disappear. Google, Microsoft, Apple could close my account on a whim, good luck trying to get them back.

In the end, changing email address for a multitude of online accounts took longer than the entire migration. Especially with government services.


This was the surprise I enjoyed the most. Being on Android, I feared the idea of having to look for good apps that can support cardDAV and calDAV natively. While reading Mailbox FAQs, I stumbled on an article where they suggested a FOSS app available on F-Droid called DAVx5.

It was just a matter of adding the single Mailbox account in the app and activate calDAV and cardDAV. Afterwards, the integrated Contacts and Calendar apps by Google would simply sync to it. I feel obliged to remark that I don’t have a Google account set up with my Android phone, and yet they work seamlessly with Mailbox through DAVx5 sync.

Email on Android was as easy as setting up a single account on K-9 and adding all the identities connected to my domains.

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