[Dovecot] Disallow POP3 from deleting messages

DormitionSkete@hotmail.com dormitionskete at hotmail.com
Thu Mar 21 01:40:46 EET 2013

On Mar 20, 2013, at 8:59 AM, Timo Sirainen wrote:

> On Wed, 2013-03-20 at 08:15 -0600, DormitionSkete at hotmail.com wrote:
>> My experience with IMAP over the internet with a couple of servers outside our monastery (while I was in it, and we have considerably better download speeds than upload) has always been that IMAP has always been incredibly slow.  So, I've always just allowed users to connect to the IMAP server via webmail.  It's slow, but usable.  
> Another idea: Get some cheap server from outside, use dsync replication
> to keep it synced with your internal one, and set up DNS so that users
> get directed to the fastest server. http://wiki2.dovecot.org/Replication

I LIKE this idea, but I have a few questions about it to see if it would be appropriate for our situation.  There are a few other things to consider that I didn't mention before because they did not seem relevant earlier.

First off, I'd just like to say that we have a web server set up at a location outside of our monastery that hosts all of our websites.  I'm currently in the process of building new servers to replace both it and our current email server.  So, assuming this is both plausible for our situation, and within my capabilities, I should be able to work on this at my leisure, and get the initial sync of our emails done while on the same LAN.  

So, the additional info and questions are the following:

1.)  Our download speeds are decent enough, but in addition to having poor upload speeds, we also have very strict limits on how much we are able to download.  And we use almost every bit of it every day.  We cannot get more, either.  We have unlimited downloads for four hours at night, however.  

2.)  We have very large message archives.  We basically have 95% of the emails we've received for the past 16 years.  So, the sync *must* only update items that have been changed.  Is this how it it would work?

3.)  We are currently using uw-imap with mbox.  If we switch to Dovecot, using Maildir format, will the sync only update the new messages and the header files for any folders that have been changed?

4.)  I thought I read somewhere in Dovecot's documentation last night that it has a 50 mb limit on folders.  It can't write anything larger than that.  Does this sound familiar?  (Now I can't find it!)  If so, is that for mbox?  We currently have some mbox folders whose files are significantly larger than that.  If we convert to Maildir format, where the individual messages are in their own files, could a folder contain messages totaling more than 50 MB using Dovecot?

    4a. -- Oops.  I just noticed this: "NOTE2: sdbox/mdbox mailbox formats are recommended for replication. Maildir still has some issues (although probably not noticeable in normal use)."  Should I consider this a show-stopper for syncing like this?

5.)  In the http://wiki2.dovecot.org/Replication page, would this be continuously synced each time a user sends, receives, deletes, or moves messages, etc.?  Or would it be periodically synced?  

6.)  Also, that page does not make it clear if one server is like the "master" and the other the "slave".  Do I do the same changes to both servers?

If, given the above additional information, it would not be an appropriate solution for us, this suggestion about syncing the two servers gave me another idea.  

I was thinking, "Well, I wonder if I could just sync the Inboxes?  We don't really need the folders synced.  In the highly unlikely event a person would ever need something from one of his folders, he could always just log into the (slow) monastery server through web mail and get it that way."

(When we are on the road, we are generally working real hard, and we don't answer any more emails or do any other computer work than we absolutely have to.)

So, that led me to the idea to simply set up some message rules in procmail in our (slow) monastery server to copy any incoming messages to the server offsite in addition to delivering them locally.  For the most part, that would be sufficient for us -- and considerably easier.  

The only downsides to this are that when we reply to messages, they would not be marked as having been replied to, and we wouldn't have copies of our replies on our main server.

The not being marked as replied to is not a big deal.  I know we could manually copy any sent messages from one server to the other when we returned to the monastery, if we really wanted to, but does anyone know of a better way to do it?

On Mar 20, 2013, at 3:11 PM, Robin wrote:

> Your main concern sounds like performance from users who connect from outside of your enterprise network, which may happen even when your mobile devices are on site, due to the way they obtain their connectivity? 

We are located deep in the Colorado Rocky Mountains.  There are only a few places a person can stand in our monastery and get cell phone reception, so I don' think that is really an issue for us.

I'd greatly appreciate any advice or information about this.  Both of these servers we're replacing are quite old.  One is 10 1/2 years old...  As I'm building the new ones, I'm trying to make things better.  Email is one of the areas I think we should be able to make big improvements on.  

So, any help will be greatly appreciated!

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