You can view email headers in FairEmail by opening an email, then using the "..." menu above the message text, and selecting "show headers".

I'm using the FDroid version of K9. What do you like from FairEmail over K9?

One great feature is that when you add images in FairEmail, it removes metadata, renames the file and other privacy-preserving data.

Unless that is optional, it's a bug, not a feature. Attachments should never be manipulated unless asked.

It prompts you every time and can be configured to have a default option.

I've been on the Google Play version of K9 for years and I must say that it was perfectly fine. I changed to FairEmail as I thought having a very old version of an email client might not be ideal from a security perspective. At the moment the biggest change from my workflow is the UI, which looks better that the old K9. Now I am not switching to K9 F-Droid version just because I am lazy to configure everything again another time.

But please bear in mind that my way of using email on my phone is very minimal. I usually just need something to read and for most of my productivity task I use mutt.

We had a HN thread a few weeks back on the K-9 Donations blog, basically the K-9 Play version is still the old client UI (but the betas are not 100% feature complete); you can opt-in to the K-9 beta on Play or F-Droid and get the new UI experience if some features like IMAP IDLE are not that important to you. (side comment, the new K-9 betas allow export/import of settings but not sure about the older version you're currently using)

The old ones have export/import as well.

K9 has an export settings feature.

I realise that this is not a common use case, but FairEmail is the only e-mail client I could find that supports TLS client authentication.

Does K9 not do this? I am certain it works with STARTTLS, it’s what I’m currently using.

Do you mean just straight TLS connection at the start of session?

I assume they're referring to TLS client certificate authentication support. As you say, most email clients can handle TLS.

Few can handle authenticating to the server with a client certificate, but FairEmail seems to support it fine, although I've yet to configure it on my own server as it's likely to break other clients that don't support it.

If it (K9) does, I certainly did not find a way to do it. Yet, it does not mean just straight TLS connection at the start of the session. Rather, it means that when the client (FairEmail, in this case) performs the handshake, it also sends its own certificate that the server can verify prior to finishing the handshake, therefore adding an extra layer of security.

Just to emphasise, this is probably not something that most people would ever need, but is certainly an important feature to me and something that FairEmail supports and apart from a rare few, nobody else does.

Same here. I switched from k9 to bluemail to fairmail. Bluemail was good but proprietary solution. Fairmail is almost as good as bluemail. Though I still looking for 'share' email with an todo list app. Fairmail and Joplin works but Joplin is not my preferred to do app.

When viewing a message, you can tap on the '...' below the address information and near the buttom of the menu will be a show headers option as well as an option to show the raw message.