My webhosts installed Horde as the webmail client, but it is quite terrible in comparison to modern software like Gmail, and its very slow.
I installed the Free and opensource RoundCube via FTP, but probably due to its mail exchange protocol (IMAP) it doesn't always show received mails, and works unreliably.
What else can I try?
Have you used any FTP-installable webmail software with success?
squirrelmail should work ok, though you'll have to edit 2-3 cfg files roundcube requires a database, if I am correct