offline-imap for backup (2010 edition)

chris coleman christocoleman at
Tue Oct 11 23:30:06 BST 2011

On 11 Aug 2010, at 01:20, Anthony DiSante wrote:
> On 08/10/2010 06:53 PM, Ng Oon-Ee wrote:
>> On Tue, 2010-08-10 at 22:30 +0200, Michael Williams wrote:
>>> Has there been any changes to the suitability of offline-imap for backup (rather than bidirectional sync) since it was discussed on this list in 2007:
>>> As discussed then, bidirectional sync risks user error/filesystem problems being catastrophically propagated upstream. A couple of rather hacky and fragile workarounds were suggested (including taking a backup of the backup, and checking the backup for changes since the last time offlineimap was run before allowing offlineimap to run again).
>>> It seems, however, that the most robust place to implement this would be in offlineimap itself. Any plans/news there?
>>> As far as I can tell, no other tool is ideally suited to this (see imapgrab (a wrapper around getmail) comes closest, but does not retain read/replied/etc. flags, i.e. it is not an exact copy.
>> If you haven't noticed, the maintainer has announced his retirement from
>> this project, and as yet noone else has stepped up to take over.
> Well, I'd be interested in this one-way mode too.  I'm currently using offlineimap, both for backup, and for a way to get local copies of all my email for the purpose of running various scripts when certain emails come in.  I never modify the data directories, but I didn't consider the possibility of filesystem corruption causing problems to propagate up to the live mail on the server.
> I haven't looked at the offlineimap code, and I'm more of a Perl hacker than a Python one; but doesn't it seem like, at least in theory, it'd be easy -- perhaps even trivial -- to prevent it from writing anything back to the server?

Since offlineimap is being more actively developed, has there been any progress since last year?


Hi Mike

OfflineIMAP does its work in two steps: 
1) copy mail down from remote server, saving it on the local folder (or local imap server) and the local message status flags cache.  
2) copy local mails from the local folder (or local imap server) up to the remote server, saving status changes again in the local message status flags cache.

So it looks like just doing step 1 would accomplish what you want - a one-way backup.  With the warning that you could be overwriting some flags in the local message status flags cache - in other words, any changes to the message status flags, between backups, could be lost. Probably not a big deal when you're doing a one-shot backup.

It's really simple - Nicholas or Sebastian might have included this feature already - you should to put in a feature request just in case it's not.
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