Domain Switch & Leaving Posteo Behind

Recently I switched my domain name (though flosch.at will still continue to work for a few months) as well as my main mail address & provider. This change came quite rapidly, but I think in one way or another it makes sense as a next step from where I started.
In this blog post I'll try to layout the reasoning behind my decision.

The realisation

It all started when a colleague of mine recently started to research e-mail providers, which value his privacy more than his current one (which aren't hard to find if your provider is called Google). As far as I know he still hasn't decided which one he wants to go for, but ProtonMail and Posteo are strong contestants.
Anyway, we talked about pros and cons of different e-mail providers and I did some research on my own to find arguments for the mail provider of my choice, which I've been using for the past 5 years already, called Posteo.
In my opinion Posteo was (and for most people still is) a totally fine choice. It only uses open source software, provides a strong, optional encryption concept, also offers calendar as well as contact sync and is as cheap as a trustworthy mail provider gets (1€ per month).
One argument against it, though, which I encountered several times online, is that it does not support using your own domains. This means that you are bound to use the ones that Posteo provides (which are all in the format of @posteo.*, where * is about any TLD you can imagine).
That didn't bother me back when I created my Posteo account, but now that I've read the discussions it caused, it got me thinking.
I didn't mind that Posteo owned the domain, I trust them enough to let me keep my e-mail address as long as they exist. But that's the point: as long as THEY exist, not me. If they cease to exist, which is not the most unlikely scenario I could imagine (see Lavabit), I would be most utterly fucked.
I'm not sure if I would be able to change my mail address all of a sudden at all the services that I use. At the very least it would a job so cumbersome to do, that I would probably curse myself multiple times.
After this realisation, I kept finding additional reasons why it could be a bad idea to lock yourself into one specific provider. For example, they could also increase the prices to exorbitant levels (I also would not assume they would do anything as bad as this) and I simply would have to pay, as I could not change my mail in time.
And finally, what if i just want to switch provider for the sake of it? What if some other provider simply offers some fancy cool feature that I would like to try out? Or offers a better looking interface and/or app (a topic I particularily have an eye on as mobile developer)? I couldn't switch.
After having spent so much time researching the more privacy-conscious and open solutions for my needs, I locked myself into one mail provider.

Consequences

I already had a domain (flosch.at), but I didn't like it as much as I did when I first registered it. And now that I started to think about using it as my mail address, I liked it even less. So the first thing i had to do, was to find a new domain, which I would also be fine with to use it as mail address.
One important thing was that it had to be short. I don't want to type my full name into the command line, nor do I want it at the end of my e-mail address. So, I did some research on available top level domains and tried to find some, which cleverly mix with my name and the TLD to make it short. At first I didn't find any, but then I discovered the finnish top level domain .fi.
Whenever there are multiple Florians in a group I'm part of, people tend to refer to to me using a nickname version of my lastname: Schrofi . I checked and found that schro.fi was still available, a rather cheap domain and it ticked all the boxes, so I purchased it.
Setting up the new domain for my website was a piece of cake, I just updated the DNS records to point to my IP, updated the nginx configuration, ran certbot to get SSL certificates and it was good to go.
Now I only had to find a new mail provider and setup mailing correctly (which I've never done before).

Research again

One thing was certain: I do not want to run my own mail server. Mail is just too important to risk that i do something wrong (=stupid) and will not be able to receive any mail (and yes I know about mail-in-a-box).
Additionally, I would argue, that most mail providers probably even cost less than running your own server would, if you keep it running for the sole purpose of hosting your mail (which I would do, to make sure it does not interfere with anything).
So, that out of the way, I started researching again to find a mail provider which supports custom domains.

The important features I was looking for were:

• supports custom domains
• offers calendar & contact sync
• does not cost more than 30 - 40€ per year

This limited my choices by quite a bit. Protonmail does not offer a calendar at the moment and additionally costs more than 3 times as much as Posteo, so it was out of the question.
Tutanota does not offer a calendar nor contact sync (though the first is planned to be released soon).
The ones that were closest to my requirements were Mailfence and Mailbox.org.
While I think Mailfence would have done an equally good job to host my mail, I simply went for Mailbox.org just because I liked the user interface better.

Setting it up

Contact and calendar sync were seamless. I exported everything from Posteo, imported it on Mailbox.org, changed my account in DAVx⁵ and off we go. Configuring the custom domain was a bit trickier, but good thing the Mailbox.org wiki provides an extensive step-by-step tutorial on how to set it up with their service.
After following these steps and also cross checking with CodingHorrors blog post about emails, I managed to pass all checks from Port25's authentication verifier service.

==========================================================
Summary of Results
==========================================================
SPF check: pass
"iprev" check: pass
DKIM check: pass
SpamAssassin check: ham

This seems to be good enough for most mail providers, but not for Outlook.com. For whatever reason each and every one of my mails ends up in the spam folder, eventhough I explicitly whitelisted the sender and marked the mail as "not spam".
Apparently, other mailbox users are having the same issue. I'm still not sure if it is related to my custom domain being unknown to Outlook's mail system or mailbox.org e-mails being classified as spam in general.
Anyway, I will keep watching this issue closely and hopefully it will resolve automatically. For now I'm occupied changing all of my accounts to point to my new e-mail address, knowing that this should be the last time I will ever have to do this.