[Dovecot] Shared Mailboxes, Per User SEEN flag and Mailing lists

[Peter Fern]

Personally I use postfix as it provides me with good performance and 
high flexibility, but exim should perform fine for you.  This shouldn't 
have any effect on your virtual folders.

Reikan - Sidney Ferreira wrote:

>     Well, I carefully readed all this mail and also readed about the 
> Hard and Soft linking methods.
>     This is exactly what I was looking for, so, I'll have Dovecot in 
> my project.
>     Im just wondering about SMTP, does Exim is a good choice? Will the 
> SMTP change anything about the shared box system?
>
> Peter Fern wrote:
>
>> Are you familiar with symlinking/hardlinking under unix?  If not, 
>> it's fairly straight forward, and yes - they are like file aliases.  
>> I suggest you google for it to see how it works, or 'man ln'.  You'll 
>> need to understand this to make the solution below work.
>>
>> For your scenario, linking individual files into user's mailboxes 
>> probably isn't the best method - better to use the inbuilt shared 
>> folder support in dovecot.  There are two methods of provisioning 
>> shared mailboxes in dovecot - using the namespace configuration 
>> directives, or symlinking the folders in.  The namespace method will 
>> make shared folders available to *all* mail users, so if you want 
>> opt-in/-out you'll need to use the symlink method, so for your setup, 
>> this would be the easiest method.
>>
>> A quick outline on how to make this happen:
>>
>> 1.  Create a central store somewhere containing your folders to be 
>> shared.
>> eg:
>> /var/mail/public/.MySQL
>> /var/mail/public/.PostgreSQL
>> etc...
>> 2.  In each of these folders create a file called 'dovecot-shared' 
>> and set file permissions to 0644 and set the group to one that your 
>> mail users will be members of - this will determine the permissions 
>> of mails within the folder.
>> 3.  When a user signs up to the folder, create a symlink to the 
>> relevant folder under the user's maildir.
>>
>> Then just drop mails into these maildirs.  This is all a little 
>> off-the-cuff, so if anyone disagrees yell out.
>>
>> Cheers,
>> Pete
>>
>> Reikan - Sidney Ferreira wrote:
>>
>>>     Well, here's an example of what I have in mind:
>>>
>>>     Suppose a programmers server, each one has Inbox, Outbox, etc. 
>>> Now, we also have the following shared boxes: C/C++, PHP/Perl, 
>>> HTML/CSS, MySQL, PostGreSQL.
>>>     Each user may signup for one or more of this shared boxes, being 
>>> able to mark what they read and what they didn't read.
>>>     The reason, as I said, is to sabe space. Imagine 12000 users, 5 
>>> mailboxes, 2 messages a day, it would be 117MB a day!
>>>     If I understood properly (what I don't think I did), this 
>>> hardlink would be like the file aliases, so, I woul have 1 original 
>>> message of 1KB and 12000 aliases to this message, wich wouldn't use 
>>> much space.
>>>     The main point is that I want make it all web based, so, no 
>>> downloading-and-deleting work, but, syncronizing.
>>>
>>>     I hope this help you to help me ^^
>>>
>>> Peter Fern wrote:
>>>
>>>> If all you need is to deliver a single mail to many users at once, 
>>>> you might consider hardlinking the message into the mailbox - you 
>>>> may lose a little space (never more than one block) as the filename 
>>>> entry in the filesystem will require nominal space, but it's likely 
>>>> to be quite efficient.  Symlinking won't use any additional 
>>>> filespace for each link, but will use inodes... I'm not sure 
>>>> whether dovecot will handle a symlink for an actual mail message 
>>>> though - I would assume not.  In any case, this will only work 
>>>> properly if you are using maildirs, but then if you're not, why 
>>>> not? ;)
>>>>
>>>> Alternatively, the 1.0 series of dovecot does support shared 
>>>> folders, and I believe per-user flags are supported, though I'd 
>>>> like someone to confirm?  Again, this will only work easily on 
>>>> maildirs due to filesystem permissions and such...
>>>>
>>>> Reikan - Sidney Ferreira wrote:
>>>>
>>>>>     Hi!
>>>>>     Im making a small research about IMAP servers and it's 
>>>>> features. As the subject suggests, I want make a shared mailbox, 
>>>>> with per user \seen flag to work like a mailin-list works.
>>>>>     The reason to use 1 shared folder is simple: Imagine 12k users 
>>>>> sending 1KB messages each week, it will be 12+ MB of useless 
>>>>> information.
>>>>>     Many people told me that IMAP could do this, but now seem that 
>>>>> it is a little harder then what they made it look like.
>>>>>     Finally, some EXIM users told me that Dovecot could handle it 
>>>>> a little better than Courier, so, Im here to try to find more 
>>>>> information about it.
>>>>>     Follows the mail that I received from an EXIM user.
>>>>>
>>>>>         Sidney
>>>>>
>>>>> Bill Hacker wrote:
>>>>> > Reikan - Sidney Ferreira wrote:
>>>>> >
>>>>> >>     Does Exim works as IMAP?
>>>>> >>     Does it allow public folders?
>>>>> >>     The SEEN control is made by USER or MESSAGE?
>>>>> >>
>>>>> >>
>>>>> >
>>>>> > Exim is an MTA, not an IMAP (or POP) server.
>>>>> >
>>>>> > It works well with most, perhaps all, POP and IMAP servers.
>>>>> >
>>>>> > Two widely-used IMAP partners are courier-IMAP and Dovecot.
>>>>> > Both of these support POP as well as IMAP.
>>>>> > There are several others known to work.
>>>>> >
>>>>> > Folder sharing can be complex.  IMAP is more appropriate than 
>>>>> POP, even
>>>>> > if other users are on POP.
>>>>> >
>>>>> > Exim can use Maildir MBox, and other storage types, can use 
>>>>> several at
>>>>> > once, can select  the storage location, storage type, UID, GID, and
>>>>> > privilege mask from hard-coded, flat-file, db or RDBMS lookup, 
>>>>> and can
>>>>> > create the storage if it does not already exist.
>>>>> >
>>>>> > All/any of the above can be done on a per-user, per-domain or 
>>>>> per-sender
>>>>> > basis, and/or on combinations of the above.
>>>>> >
>>>>> > The rest is up to the IMAP and client configuration(s).
>>>>> >
>>>>> > Dovecot can handle Maildir, MBox and other.  Courier-IMAP is 
>>>>> optimized
>>>>> > for Maildirs.
>>>>> >
>>>>> > Message state assignments are the responsibility of the 
>>>>> retrieval agent
>>>>> > (IMAP/POP + MUA).
>>>>> > The MTA is not involved once the message has been delivered to 
>>>>> storage
>>>>> > 9or distant server).
>>>>> >
>>>>> > As an MTA may process multiple valid messages per valid 
>>>>> connection, not
>>>>> > all for the same valid user, or even same destination server, 
>>>>> Exim does
>>>>> > routing and delivery in an area that is essentially per-user OR
>>>>> > per-destination sensitive, but always per-message relevant, i.e. -
>>>>> > normally handled one at a time at the 'decision making' points.
>>>>> >
>>>>> > HTH,
>>>>> >
>>>>> > Bill Hacker
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