[Dovecot] Keep pop messages, is it possible?

[Bill Cole]

At 8:23 PM -0800 1/14/08, Jeff Grossman wrote:
>Fábio M. Catunda wrote:
>>Hi!
>>
>>I would like to find a way to not delete 
>>messages when they are downloaded via pop3, is 
>>that possible with dovecot?
>>
>>Gmail do this, I dont know how they mark 
>>messages that have been downloaded to avoid 
>>clients to download it again, but it looks like 
>>a good resource!
>>
>>Thanks for the help!
>That is a feature of the client.  Most clients 
>have a setting which says "Keep Messages On 
>Server".

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.

-- 
Bill Cole                                  
bill at scconsult.com