[LINK] RFI: Email Duplicate-Download Problems

[David Lochrin]

On 2015-08-01 10:38 Roger Clarke wrote:

> After I download using IMAP from Linux/Evolution, the next time I download on the primary (OSX/Eudora/POP), I get all 7 days' worth of emails still stored at the ISP.  This duplicates of the order of 1000 messages and makes a complete mess of my carefully organised suite of mailboxes.
> 
> This kind of issue has also occurred when using webmail.  However, my son successfully uses webmail and Eudora concurrently and *without* this same issue. 
> 
> I don't understand what the mechanism is that causes the mail-server to lose its record of what has been downloaded before.

I have been using exactly that process for some years now without any problems.  My primary system is SuSE Linux running KDE mail and the other one is a Windows-7 system running Thunderbird, both using POP3.

The problem may arise because IMAP doesn't delete downloaded emails automatically by default, but you should be able to configure your IMAP client to delete each one after it's successfully downloaded.

I see there's an article comparing IMAP & POP on Wikipedia (where else?) which seems quite good - see
https://en.wikipedia.org/wiki/Internet_Message_Access_Protocol

This article states: "IMAP supports both on-line and off-line modes of operation. E-mail clients using IMAP generally leave messages on the server until the user explicitly deletes them.  This and other characteristics of IMAP operation allow multiple clients to manage the same mailbox.  Most e-mail clients support IMAP in addition to Post Office Protocol (POP) to retrieve messages; however, fewer e-mail services support IMAP.[3] IMAP offers access to the mail storage.  Clients may store local copies of the messages, but these are considered to be a temporary cache.[4]"


When migrating back to the Highlands I export everything in Thunderbird's outbox to a memory stick and import the lot later on my primary system.  But be aware that when emails are saved in mailbox (.mbox) format then "deleting" them only marks them as deleted, and exporting the whole folder will probably export the lot.  It's necessary to compact the folder in order to get rid of them entirely.

Hope this helps...

David L.