I have been using mail programs for years but recently I find myself using the server-side Roundcube program. I have a few accounts and I am annoyed when I have to type user/pass all the time.
Is there a possibility to create a link which would automatically log me in an account?
BT do not provide a link generally speaking to Auto-Logon to an account as such. Are you using the Roundcube program to manage BT mailboxes?
Apart from using the general settings for BT Office 365 Mailboxes (settings info can be found here) there is little BT can do to assit.
Have you tried looking up the support forums for the Roundcube program? Some information might be found there - that link being here
Hope this helps.