I have a small mail server set up using postfix and dovecot. All is well; I have proper certificates, multiple isolated users, etc.
However, when sending a message from Thunderbird I get an error: "There was an error saving the message to Sent Messages. Retry?". I have tried all of dovecot's mail storage configurations, but the error persisted. What am I overlooking?
I suspect it has something to do with the ability of the client to create new folders over IMAP, but I wouldn't know how to grant clients that ability.
As for the nature of my system: I basically followed this tutorial, but on Debian 9.