Re: [courier-users] Management of maildir structures

[Sam Varshavchik]

Lindsay Haisley writes:


On Mon, 2016-07-25 at 06:22 -0400, Sam Varshavchik wrote:
> new/cur split was meant to be merely a means to identify messages that  
were  
> seen for the very first time. Nothing more than the means to notify the  
user  

> "you have X new messages". This is not the same thing as how many unread  
> messages there are. Messages in cur may still be unread.

Sam, I made one further small change to the Wikipedia paragraph on
maildirs, which now states:

"When a maildir reading process (either a POP or IMAP server, or a mail
user agent acting locally) finds messages in the new directory it
_must_ move them to cur ... etc."

I did a bit of research on the term "mail retrieval agent" and it
doesn't look as if this is an apt description of a POP or IMAP daemon,
so I changed the wording to be more specific.

Is this technically correct, and is "must" appropriate?


I agree, this is technically correct.



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Re: [courier-users] Management of maildir structures

[Lindsay Haisley]

On Mon, 2016-07-25 at 06:22 -0400, Sam Varshavchik wrote:
> Alessandro Vesely writes:
> 
> > What is still missing is the purpose.  I grasp that MRAs and MUAs have a 
> > duty
> > which rsync is relieved of, but why?  (A similar duty is to delete any old  
> > file
> > left behind in tmp.  This is just housekeeping which any process can do.)
> >
> > Rather than classifying maildir readers any further, it may be clearer to
> > explain, say, that such new-cur split is/was meant to ease some sort of
> > operations, such as client-side spam filtering.  IMAP and POP3 client don't
> > seem to need such functionality, so it must have been something related to
> > local MUAs.  Is that right?
> 
> new/cur split was meant to be merely a means to identify messages that were  
> seen for the very first time. Nothing more than the means to notify the user  
> "you have X new messages". This is not the same thing as how many unread  
> messages there are. Messages in cur may still be unread.

Sam, I made one further small change to the Wikipedia paragraph on
maildirs, which now states:

"When a maildir reading process (either a POP or IMAP server, or a mail
user agent acting locally) finds messages in the new directory it
_must_ move them to cur ... etc."

I did a bit of research on the term "mail retrieval agent" and it
doesn't look as if this is an apt description of a POP or IMAP daemon,
so I changed the wording to be more specific.

Is this technically correct, and is "must" appropriate?

-- 
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FMP Computer Services |
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Re: [courier-users] Management of maildir structures

[Lindsay Haisley]

On Mon, 2016-07-25 at 09:43 +0200, Alessandro Vesely wrote:
> What is still missing is the purpose.  I grasp that MRAs and MUAs have a duty 
> which rsync is relieved of, but why?  (A similar duty is to delete any old 
> file 
> left behind in tmp.  This is just housekeeping which any process can do.)

rsync and "mail retrieval agents" (this actually isn't the right term
either) are TOTALLY different animals. The difference lies in the fact
that software agents such as imapd and pop3d are designed to be part of
a mail processing chain. The input to these agents is a mail storage
structure, mbox, maildir, maildir++ or whatever. The output is designed
to conform to a RFC-standardized communications protocol (IMAP, POP3).
These protocols deal with _messages_ and are independent of the details
of the mail storage structure. rsync, on the other hand, is a file
management utility which should make faithful reproductions of file
system structures. It doesn't know a maildir from a website or a python
library.

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Re: [courier-users] Management of maildir structures

[Sam Varshavchik]

Alessandro Vesely writes:


What is still missing is the purpose.  I grasp that MRAs and MUAs have a duty
which rsync is relieved of, but why?  (A similar duty is to delete any old  
file

left behind in tmp.  This is just housekeeping which any process can do.)

Rather than classifying maildir readers any further, it may be clearer to
explain, say, that such new-cur split is/was meant to ease some sort of
operations, such as client-side spam filtering.  IMAP and POP3 client don't
seem to need such functionality, so it must have been something related to
local MUAs.  Is that right?


new/cur split was meant to be merely a means to identify messages that were  
seen for the very first time. Nothing more than the means to notify the user  
"you have X new messages". This is not the same thing as how many unread  
messages there are. Messages in cur may still be unread.




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Re: [courier-users] Management of maildir structures

[Alessandro Vesely]

On Sun 24/Jul/2016 16:19:40 +0200 Lindsay Haisley wrote:
>>>
>>> rsync doesn't qualify as a "mail retrieval agent".

It can be used to retrieve mail, despite its missing qualifications.  And it 
must skip tmp, lest fetch rubbish.  So there is a class of maildir readers 
which are neither mail retrieval agents nor mail user agents.

> I modified the Wikipedia paragraph to say:
>
> When a maildir reading process (either a mail retrieval agent or a
> mail user agent acting locally) finds messages in the new directory
> it must move them to cur (using rename() - link then unlink strategy
> may result in having the message duplicated) and appends an
> informational suffix to the filename before reading them.

What is still missing is the purpose.  I grasp that MRAs and MUAs have a duty 
which rsync is relieved of, but why?  (A similar duty is to delete any old file 
left behind in tmp.  This is just housekeeping which any process can do.)

Rather than classifying maildir readers any further, it may be clearer to 
explain, say, that such new-cur split is/was meant to ease some sort of 
operations, such as client-side spam filtering.  IMAP and POP3 client don't 
seem to need such functionality, so it must have been something related to 
local MUAs.  Is that right?


Ale
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Re: [courier-users] Management of maildir structures

[Lindsay Haisley]

On Sun, 2016-07-24 at 08:47 -0500, Lindsay Haisley wrote:
> On Sun, 2016-07-24 at 08:41 -0500, Lindsay Haisley wrote:
> > 
> > I don't think this is quite correct either. rsync operates at a file
> > level and should NOT move messages from new to cur. The distinction
> > should specify that a "mail retrieval agent" operating directly on a
> > Maildir MUST (not MAY) move files from new to cur. This includes a MUA
> > operating on a _local_ Maildir, as well as a daemon such as impad or
> > pop3d, all of which provide a message level interface in the mail
> > handling stack. rsync doesn't qualify as a "mail retrieval agent".
> The term "mail retrieval agent" should be linked to 
> ia.org/wiki/Mail_retrieval_agent> although this article could also
> stand some improvement since it gets the relative functions of a MDA
> and a MRA in the mail management chain somewhat out of sync.

I modified the Wikipedia paragraph to say:

When a maildir reading process (either a mail retrieval agent or a
mail user agent acting locally) finds messages in the new directory
it must move them to cur (using rename() - link then unlink strategy
may result in having the message duplicated) and appends an
informational suffix to the filename before reading them.

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Re: [courier-users] Management of maildir structures

[Lindsay Haisley]

On Sun, 2016-07-24 at 08:41 -0500, Lindsay Haisley wrote:
> I don't think this is quite correct either. rsync operates at a file
> level and should NOT move messages from new to cur. The distinction
> should specify that a "mail retrieval agent" operating directly on a
> Maildir MUST (not MAY) move files from new to cur. This includes a MUA
> operating on a _local_ Maildir, as well as a daemon such as impad or
> pop3d, all of which provide a message level interface in the mail
> handling stack. rsync doesn't qualify as a "mail retrieval agent".

The term "mail retrieval agent" should be linked to  although this article could also
stand some improvement since it gets the relative functions of a MDA
and a MRA in the mail management chain somewhat out of sync.


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Re: [courier-users] Management of maildir structures

[Lindsay Haisley]

On Sun, 2016-07-24 at 11:40 +0200, Alessandro Vesely wrote:
> However, the sentence became obviously false after that change.  So I also 
> alleviated the duty of a maildir reader by s/moves/may move/.  The sentence 
> now 
> reads:
> 
>     When a maildir reading process finds messages in the /new/ directory it
>     may move them to /cur/
> 
> For example, consider rsync building a backup archive of a maildir.  It is 
> obviously a maildir reader, clearly not an MUA.  I'd say it shouldn't read 
> tmp, 
> but I don't think it should move new to cur.  OTOH, MUAs display unread mail 
> subjects in bold irrespectively of the directory they're in.  What's the 
> purpose of having new and cur, then?

I don't think this is quite correct either. rsync operates at a file
level and should NOT move messages from new to cur. The distinction
should specify that a "mail retrieval agent" operating directly on a
Maildir MUST (not MAY) move files from new to cur. This includes a MUA
operating on a _local_ Maildir, as well as a daemon such as impad or
pop3d, all of which provide a message level interface in the mail
handling stack. rsync doesn't qualify as a "mail retrieval agent".

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Re: [courier-users] Management of maildir structures

[Alessandro Vesely]

On Sun 24/Jul/2016 00:12:34 +0200 Sam Varshavchik wrote:
> Lindsay Haisley writes:
>> On Sat, 2016-07-23 at 13:29 -0700, Gordon Messmer wrote:
>>> In this case, I think that "MUA" simply means "the process that's
>>> reading the mail dir."  In particular, it refers to Dovecot in the
>>> same paragraph.
>>
>> Well you may be right, except that "mail user agent" in that paragraph
>> is a link to a Wikipedia article which is pretty specific that the term
>> refers to an "email client" or "email reader".

Agreed.  The paragraph "When the mail user agent process finds messages in the 
/new/ directory [...]" was added on 14 October 2005.  It uses wrong terms.
https://en.wikipedia.org/w/index.php?title=Maildir=next=68789841

> I would agree that "MUA" refers to anything that reads a maildir, in the most
> liberal interpretation.

Hmm... it's bad to use the same name for different things.  I changed MUA to 
"maildir reading process".  (I don't think we need a specific name for such 
kind of things.)

However, the sentence became obviously false after that change.  So I also 
alleviated the duty of a maildir reader by s/moves/may move/.  The sentence now 
reads:

When a maildir reading process finds messages in the /new/ directory it
may move them to /cur/

For example, consider rsync building a backup archive of a maildir.  It is 
obviously a maildir reader, clearly not an MUA.  I'd say it shouldn't read tmp, 
but I don't think it should move new to cur.  OTOH, MUAs display unread mail 
subjects in bold irrespectively of the directory they're in.  What's the 
purpose of having new and cur, then?

Ale
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Re: [courier-users] Management of maildir structures

[Sam Varshavchik]

Lindsay Haisley writes:


On Sat, 2016-07-23 at 13:29 -0700, Gordon Messmer wrote:
> In this case, I think that "MUA" simply means "the process that's
> reading the mail dir."  In particular, it refers to Dovecot in the
> same paragraph.

Well you may be right, except that "mail user agent" in that paragraph
is a link to a Wikipedia article which is pretty specific that the term
refers to an "email client" or "email reader".

I think my assumption is a safe one.  Thanks.


I would agree that "MUA" refers to anything that reads a maildir, in the  
most liberal interpretation.


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Re: [courier-users] Management of maildir structures

[Lindsay Haisley]

On Sat, 2016-07-23 at 13:29 -0700, Gordon Messmer wrote:
> In this case, I think that "MUA" simply means "the process that's
> reading the mail dir."  In particular, it refers to Dovecot in the
> same paragraph.

Well you may be right, except that "mail user agent" in that paragraph
is a link to a Wikipedia article which is pretty specific that the term
refers to an "email client" or "email reader".

I think my assumption is a safe one.  Thanks.

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FMP Computer Services |   chooses its friends."
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Re: [courier-users] Management of maildir structures

[Ben Kennedy]

> On 23 Jul 2016, at 12:05 pm, Lindsay Haisley  wrote:
> 
> I've run into a couple of articles, including the Wikipedia article at
>  on maildirs which state that
> the internal management of files in the new, tmp and cur directories is
> the responsibility of the client's MUA ("When the mail user agent (MUA)
> process finds messages in the new directory it moves them to cur (using
> rename()"). This makes no sense.

Maybe it's just alluding to clients that deal in Maildirs on their local file 
system (e.g. pine or elm?*), whereas the same is also implied for pop3/imap 
services?

b

* (since it's been >10 years since I last used a remote command-line mail 
client I can't remember if those dealt in Maildirs or just mbox, but the idea 
stands)


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Re: [courier-users] Management of maildir structures

[Gordon Messmer]

On 07/23/2016 12:05 PM, Lindsay Haisley wrote:

the Wikipedia article at
  on maildirs which state that
the internal management of files in the new, tmp and cur directories is
the responsibility of the client's MUA ("When the mail user agent (MUA)



In this case, I think that "MUA" simply means "the process that's 
reading the mail dir."  In particular, it refers to Dovecot in the same 
paragraph.


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