I have been using K9 for a long time on Android. No complaints. I guess most Apple users will simply use the default email client, which works well and is probably better integrated and has a better UI than Thunderbird.
On Linux desktop, Thunderbird is still the best all around email/CardDAV/CalDAV client it seems, despite being unreasonably heavy.
On Linux desktop, Thunderbird is still the best all around email/CardDAV/CalDAV client it seems, despite being unreasonably heavy.