Thanks for the suggestion. I’ve not tried that yet because I understand that it relies on Haiku’s default Mail app to set up mail accounts and it doesn’t work well with some IMAP accounts I use such as Fastmail and Vivaldi.
After that, I tried Beam and then Icedove and I was relieved to see that Icedove was able to get all my IMAP accounts working until suddenly my accounts and messages suddenly disappeared and there was no way to get it back to normal. Anyway, since then I’ve resorted to using webmail on Haiku and more or less given up on mail user agents…