When it comes down to the best of the best digital communication systems in 2026: I find the best is e-mail actually. You can pick your platform and you can run it on just about any device without any real issue.

DeltaChat is a software that in the front-end appears to be a typical messenger app, but it in fact behind the scenes uses e-mail infrastructure along with OpenPGP, Autocrypt, and SecureJoin to provide secure, encrypted instant messaging. I like the desktop and mobile clients, and how they work well together. I just never really liked how alt tech clients handle push notifications. These apps seem to be poorly optimized and destroy batteries on mobile devices.

Then there is the cross-platform messaging like WhatsApp, Signal or Telegram. I think that these have their perks, but they just seem to lack the lightweight front-end that XMPP clients tend to have. XMPP as a protocol is really versatile and useful, but the clients that exist around it lack consistency (and the mobile clients suffer the same issues that DeltaChat encounters).

I can touch on other communications software, like Discord or other social media direct messaging/messengers, but I find the same flaws with those as I do with the big cross-platform messaging services.

I also miss the old school IM software of the late 90s and 2000s too. Software, even if it looked kinda bulky and/or boring, was a bit more enterprise-ready than even some of the enterprise communications systems that exist today (Teams, Zoom, etc). I feel like MSN messenger had a lot more dependability in its UI than Teams' clunky-ness that I found even on Windows.

IRC is cool too, but not really sure why I'd want to check on idle village on my phone too.

And then we can talk about SMS: where the Blue vs Green clash. That has got better over the years, from what I hear, but most of the world tends to just use WhatsApp or other cross-platform to alleviate the clash of different devices. Of course, another issue is that I think only the Apple ecosystem really handles SMS across all types of devices well.

When all is put aside, it just seems that e-mail inevitably is preferable to me. Many different e-mail clients exist, so doesn't really matter what you want to use or what I want to use. And it just seems that it can built upon further and further. (DeltaChat shows us a potential use/extension of e-mail) Only flaw I can find in e-mail is that self-hosting can be a bit of an ordeal to optimize, and a lot of bigger hosting structures (Outlook, iCloud, Google, etc.) kind of monopolize the "trusted" space. If Gmail becomes ubiquitous with e-mail, then I think that would be a sad day (even though the service would be more dependable than others). I don't see that day happening though, because e-mail centralization is just more of a convenience rather than a necessity or social pressure.