POP3 getting previously delivered messages.

[Tim Dickson]

On 24/07/2015 10:37, Jas Reehal wrote:
> Hi All,
>
> This is my first post to this list. I have recently upgraded to 
> dovecot version 2.2.10.
>
> 1. I have one POP3 user who does not want to delete his email on the
>    server.
> 2. He has accumulated over 19000 messages, and the 'dovecot.uidlist'
>    file has more than 19000 lines!
> 3. Occasionally now when he has received one or more new emails, and 
>    his email client does a 'get new mail' operation (POP3)
>    he begins to receive email he has already received previously.
>
> last time this happened all 19000+ messages were delivered again, 
> leaning to duplicate entries in all his mailboxes.
>
> I have reproduced this issue with a dummy email account with a POP3 
> client, leaving all messages on the server. I have delivered 20000 
> messages to this email account, each about 1.3k ins size and each  
> with ....
>
>   Subject: Message number <n>
>                       Body containing    "Message number <n>" 
>                 where <n> is 1 to 20000
>
> now occasionally if I send another message to this email account, and 
> then check for new messages using a POP3 client I get more messages 
> downloaded than I expect!
>
> The 'dovecot.uidlist' file is not corrupt, but I beleive due ti it's 
> size (number of lines) the is an issue on compiling a
> ' POP3 drop-list'. I have attached a file 'dovecot-a.txt' which shows 
> the  'dovecot -a'  output from my server.
>
> Based on what I have investigated I believe that this issue may not be 
> correlated with a migration to version 2.2.10, but more to do with the 
> number of messages retained on the server.
>
> Is there anyone who has any insight into what is happening and if 
> there is any remedy, perhaps a "pop3_client_workarounds =" or other 
> POP3 or UIDL directive in the conf files?
>
>  The user is stubbornly resisting migration to IMAP, because of the 
> time and effort he says will be required to replicate his organised 
> filing/storage of messages on the server.
>
not a fix for the technical issue, but it is very easy to delete the 
messages on the server, create an imap account on the same mua (email 
client) and then drag the emails/email folders from the pop account to 
the imap account. This will take a little while as the client instructs 
the imap server to recreate the structure server side. if you are using 
maildir format it is easy enough to check that the structure has been 
created properly. Then the pop account can be removed from the client, 
and his/her email directory structure has been preserved.
I used this method when migrating users to dovecot using imap from their 
isp using pop, when using thunderbird email client, and one of those 
users has over 24000 emails.
if using a different email client it is worth experimenting on a test 
account first.
It is also a good idea to backup the emails first "just in case".
regards, Tim
> Kind Regards  Jas Reehal
>
>