Proton Mail alternatives with a custom domain, IMAP and PGP: four providers checked
A common reason to leave a mail provider is a short list of hard requirements: your own domain, IMAP so any mail app works, and PGP or S/MIME so you keep end-to-end encryption. This page tests four privacy-minded paid providers against those three lines, using only each provider's own public pages, read on 2026-10-15. A cell is PASS when a page we read states it, FAIL when a page states the opposite, and UNKNOWN when we did not find it on the pages named. UNKNOWN is not a pass. Uptime is not tested here at all: it needs a status history, not a pricing page.
The result
| Provider and plan | Entry price (as shown) | Custom domain | IMAP | PGP or S/MIME |
|---|---|---|---|---|
| Fastmail Individual | $5/month billed yearly, $6 monthly [1] | PASS: "Use your own domains to make custom addresses" [1] | PASS: imap.fastmail.com, port 993; Basic plans do not include IMAP [2] | UNKNOWN: the pricing page says "robust encryption" without naming PGP or S/MIME [1] |
| mailbox.org Standard | EUR 4/month; Light is EUR 1 [3] | PASS on Standard and Premium; Light lists none [3] [4] | UNKNOWN: not named on the pages we read | PASS: "PGP, S/MIME and TLS" [4] |
| Posteo | 1 EUR/month [5] | FAIL: asked "Can I use Posteo with my own domains?" it answers "No" [6] | PASS: IMAP/POP3 [5] | PASS: inbound S/MIME or OpenPGP encryption, plus Mailvelope (PGP) in webmail [5] |
| Migadu Micro or Mini | Micro $19/year; Mini $9/month or $90/year [7] | PASS: its pricing FAQ says "You can have as many domains as you want" within the plan's quotas [7]; custom-domain mail is its model [8] | PASS: IMAP, POP3 and SMTP described [8] | PARTLY: no built-in PGP claimed. It says to use end-to-end tools such as GPG with your correspondents [8] |
What the table means for the three requirements
- All three PASS: none of the four, as far as the pages we read go. mailbox.org Standard is closest, with only IMAP unconfirmed on the pages named. That one is quick to settle on its help centre.
- Eliminated by a hard line: Posteo fails the custom-domain line outright, on its own FAQ. If you do not need your own domain, it passes the other two.
- Open questions: Fastmail's PGP or S/MIME support and mailbox.org's IMAP are the two cells to check on the provider's help centre before you decide. We did not find either on the pages we read, so we do not claim them.
- Migadu is a judgement call: it states it does not encrypt stored mail itself and tells people who need that to encrypt on their own side [8]. Whether that meets "PGP" depends on whether you run GPG in your mail client.
Costs that are easy to miss
- Fastmail's cheapest plan, Basic ($3/user/month yearly), has no IMAP, SMTP, CalDAV or CardDAV access [2] [1]. If you want a mail app other than Fastmail's own, you need the next plan up.
- mailbox.org bills per mailbox. Its FAQ gives the example of a family of four on Standard paying EUR 12 per month, paid annually [4].
- Migadu's limits are per account, not per mailbox: the Micro plan allows 200 messages in and 20 out per day [7]. Check that against how you send.
- Posteo starts at 4 GB of storage and charges extra above that [5].
Before you move any mail
- Write your hard lines (for example: own domain, IMAP, PGP or S/MIME, hosted in the EU) and the soft ones (price, storage, calendar).
- Drop any provider that fails a hard line in writing. Do not drop one for UNKNOWN: go and read the answer, then date it.
- Keep your current provider in the table as "stay put" until the replacement passes every hard line. Moving mail takes work: DNS (MX, SPF, DKIM), copying old mail over IMAP, and updating every account that uses the address.
- Run both for two weeks before you cancel.
The free replacement scorecard turns your hard lines into pass or fail tests in the browser and shows which unchecked cells could still change the winner. For a full worked example with a source on every cell, see the CI replacement sample. If you want this done for your own tool and requirements, the Switch Brief is $39 and delivered within 24 hours; it is AI-written research from public pages.
Limits of this page
This is a reading of public marketing and help pages on one day. We did not sign up, send mail or test deliverability, uptime, spam filtering or import tools, and we did not read Proton's pages, so nothing here compares against Proton itself. Prices change and vary by region and currency; confirm on the source before paying. This is not security advice.