It looks like that, in order to delete/remove existing email accounts in the NAS I need to get down and dirty with some command line action.
I enabled Telnet and opened the appropriate port in the NAS firewall, and had a poke about /var/etc/packages/MailServer/ and everything looks like I’d expect it to.
But the more information I read, the more questions remain unanswered.
Do I need to remove the email account from MailServer?
Or do I need to remove the email account from the associated Dovecot package?
Or do I need to remove the email account from both?
I need to read even more, obv.