Ok, I don't use acme so most of those issues don't appear for me.
Also, I do run a server so mail is delivered to my machine and I connect to it from iphones/ipads/etc etc when I want to use those devcies. Most often I just use plan9 to read mail. searching in nedmail is more limited I agree, you can only search forwards or backwards in the current mailbox for patterns that match either the header or the body; However this is enough for me. autocompleting email addresses would be a niceity, though I tend to set up aliases which I remember (I use a name I chose rather than the name the computer or some authority chose). This is imperfect and occasionally I need to lookup an adress but its rare. I think I am trying to say, my experience is better than what you had, however it is not as slick as gmail et al, however I have gotten used it plan9's email and it doesn't feel like a problem for me. Now a modern web browser, either native or running in an emulated environment would be really good... Actually I have been toying with running another raspberry Pi with Linux on it as a Chrome server. -Steve