Cheaper (€30/yr vs ~€50/yr; if you don't need custom domains, €1/mo)
More aliases (25 on mailbox, 50 on own domain. Proton has 10 TOTAL - why custom domain aliases are counted against Proton ones does not make sense to me.)
Support for any number of custom domains AFAICT (Proton Plus supports only one)
Trial account is not allowed to send emails, so fewer issues with services blacklisting proton.me and protonmail.com for spam (hasn't happened to me, but I have heard of some cases)
Can use a regular email client (security tradeoff for E2EE messages - but there already were plenty of discussions on whether E2EE has benefits, especially sending mail to other services)

[–] ramenu@lemmy.ml 2 points 2 hours ago

If you're using a custom domain, don't use Mailbox.org, see below:

https://userforum-en.mailbox.org/topic/anti-spoofing-for-custom-domains-spf-dkim-dmarc#comment-1524

[–] iturnedintoanewt@lemm.ee 1 points 4 hours ago (1 children)

Thanks. I'm on my second year in my bi-year purchase and considering options. Where's mailbox.org located and what are their privacy policies regarding government agencies requests?

[–] Avero@feddit.org 4 points 3 hours ago* (last edited 3 hours ago)

They're located in Germany and have to fulfill requests, they publish a yearly transparency report about that: https://mailbox.org/en/post/transparency-report-2024