On my phone - which is not yet a #linuxmobile one - I use the fabulous #davx5, while on my desktops the only real option for me was #Thunderbird
And while that is fine, trying using a Gnome Online Account suddenly showed me what I've been missing out so far, which is not only great native apps like #gnomecalendar , but also #gnomeshell integration, global search providers etc.
Until now - around two weeks - the experience has been awesome and it's definitely changing the way I use Gnome.