[Pkg-exim4-users] exim4 relay not permitted for MUA

[Magnus Lawrie]

Recently exim4 on a remote VPS stopped delivering mails sent from my MUA
(mutt). This MUA is using TLS encryption, with dovecot IMAP installed on
the VPS  internet mail host. The server continues to route local email
correctly and I can also still receive mail to my user account on my
client MUA. From my client machine, sending mail addressed to remote
domains results in mail going to IMAP inbox with the message "550 relay
not permitted". Exim4 on the client is configured as a smarthost. Can
anyone advise? Can this be a problem with my remote exim4.conf or local
exim config ?