Thanks for the answer Bill!
I see this a behavior as a good feature, seems like gmail just mark the
message as read when you download if via pop and the pop server consider
this information at the time to serve clients, it looks a pretty clean
solution for me.
I do agree that this is probably not compliant with pop3 protocol, but,
sometimes you can break a RFC to serve a good service and sometimes a
RFC is rewrited to agree with a good new feature (have a look in SIP
evolution).
I will try to do a plugin for that when I have time!
Thanks!
That's almost always correct: normal client-based POP3 server
retention is entirely dependent on clients that keep track of what
messages they have or have not downloaded, and some POP3 servers also
maintain a Status header so that multiple clients can look at the same
message and know whether another client has already read it.
GMail goes a bit further, in a somewhat useful fashion. Their POP3
server acts mostly like an auto-deleting server: once a message has
been retrieved by POP3, it will not be seen on later POP3 sessions,
even though it is retained in the GMail Inbox. Mail deleted by a POP3
or IMAP client is removed from the Inbox, but remains in the "All
Mail" dump as well as in whatever labelled collection it is in.
Frankly, that behavior is positively weird and arguably dysfunctional
from a POP3 perspective, but then POP3 really isn't designed with a
server-based persistent mailstore in mind.
It is my understanding that there is widespread principled aversion to
the Status header (which is understandable) so that's likely not to
happen for Dovecot. The GMail message hiding for POP3 seems to me like
a recipe for disaster for anyone not willing to provide essentially
unlimited permanent storage for mail, since it effectively hides mail
from POP3 users without deleting it.
