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List:       debian-user
Subject:    Re: Avoid POP3
From:       Miles Fidelman <mfidelman () meetinghouse ! net>
Date:       2011-05-18 20:09:45
Message-ID: 4DD42789.8050909 () meetinghouse ! net
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Camaleón wrote:
> Next time you need to configure a POP3 account tell me if you leave
> enable the "keep a copy in the server" setting. It's not the default, it
> never has been in any MUA, or not in any I'm aware of. I don't think how
> is that so hard to understand.
>    

I think everyone understand this just fine.  What I question is why this 
is relevant, other
than in confusing the OP.

>> And YES, to the extent that pop3 is still used, there are lots of cases
>> where people leave messages on their server - for example, checking mail
>> from a smartphone, then downloading and saving it later from a computer
>> at home or office.  (And, perhaps, as pointed out in RFC1918, using the
>> pop3 server as a cheap mail repository.)
>>      
> Yes, it can be used, of course, it's an optional feature that can be
> provided by your e-mail server.
>    

I see it as just the opposite.  Keeping the email until explicitly 
delete is the assumption.  Deleting
email without a specific DELE command issued is optional, and out-of-band.

>> POP3 is not intended to provide extensive manipulation operations of
>> mail on the server; normally, mail is downloaded and then deleted."
>>
>> Note the word "normally."
>>      
> Yes, I've noted, I hope you also did :-)
>    

I did.  I also note that in standards speak, "normally" is equivalent to 
"may."  What matters
are the "should" and "must" statements.  In particular, the RFC states:

"Clients MUST not assume that a site policy will automate messagedeletions,
and SHOULD continue to explicitly delete messages using the DELE command
when appropriate."  (emphasis mine)

>>
>> -----
>> Which brings us back to the original question that started this thread:
>>      
> Well, at last someone re-read the original post!
>    

:-)
> I read it as if the OP is currently *downloading and deleting* the e-
> mails that come from the POP3 server... but he can read the messages
> without downloading them, many pop3 checkers do that way! And I just said
> this, no more, no less.
>    

I read it as an OP unclear on the concept.  He (she?) is trying to 
access POP3 mail from
Roundcube - with a less than clear understanding of how POP3 works - as 
evident from
a statement that asks about "reading without downloading."

>> 2.  POP3 does NOT inherently delete messages after they are read
>>      
> It's the default action, but you can use another words if you like.
>    

It's the default action of many clients, not of the POP3 protocol.

Since the OP was asking about things like gateways, the matter of 
defaults is very
much less clear.  I expect, for example, that Blackberry's email gateway 
defaults
to leaving mail on the original account.

And then there are libraries and tools like fetchmail - where everything 
is specifiable.

>
>    
>> 3.  There are both clients and software libraries (and probably gateway
>> services) that can:
>> - pull mail from a POP3 mailbox
>> - make that mail available via IMAP
>> - AND leave the original mail on the POP3 server
>>      
> Of course, there are also fetchmail and getmail for that task and you can
> instruct both applications to keep a copy in the server.
>    

Which, I expect is really the solution to the OPs original question.

>> What also might be relevant is clarifying the original poster's intent.
>>      
> Exactly!
>    

Always :-)
>> Why is someone "building  an app which uses Roundcube to read mails" -
>> given that Roundcube already IS an app to read mails.  If the question
>> is "how do we extend Roundcube to access POP3 mailboxes?" that leads to
>> a very different answer (e.g., a plug-in or gateway) than if the OP is
>> writing an application that has email as an internal function - in which
>> case, that tends to lead toward use of a package of mail-access library
>> routines, rather than an email client like Roundcube.
>>      
> Just a side note on this.
>
> You are not aware that the OP sent the same question to the Spanish
> mailing list and I replied to him in there becasue I first saw the
> question in that list... and I asked him to clarify what was his exact
> intention, what was he wanting to get because I was not very clear to me,
> neither.
>    

Ahhh... don't you just hate that.
>> What is definitely not helpful are factually inaccurate statements like:
>> "pop3, due to its own nature, inherits by default a
>> "download/fetch/get/retrieve and delete" and then attempts to further
>> justify such statements with further inaccurate statements and with
>> references to binding documentation that states exactly the opposite.
>>      
> Sir, just two things:
>
> 1/ The "inaccurate statements" can be because I'm not a native English
> speaker and my English vocabulary is not as good as I would like (or as
> it can be yours). I hope you can understand that.
>    

Fair enough.
> 2/ The RFC (and also the Wikipedia article) clearly say that UIDL is not
> intended to be used as a "poor" copy of the imap features, that is, to
> keep messages on the server and follow their state (seen, read, etc...)
> nor to track them.
>
>    

The RFC is definitive, Wikipedia certainly is not.  I'll still go back 
to the RFC statement:

"Clients MUST not assume that a site policy will automate messagedeletions,
and SHOULD continue to explicitly delete messages using the DELE command
when appropriate."

I'll also state that I would consider it a poor design and policy for a 
server to automatically
delete messages without explicit deletion.  Lines go down, sessions get 
dropped, people
access mailboxes from multiple computers - there are lots of reasons 
that one needs to be
able to re-read a message.

> This is from Wikipedia:
>
> ***
> "(...) An extension mechanism was proposed in RFC 2449 to accommodate
> general extensions as well as announce in an organized manner support for
> optional commands, such as TOP and UIDL. The RFC did not intend to
> encourage extensions, and reaffirmed that the role of POP3 is to provide
> simple support for mainly download-and-delete requirements of mailbox
> handling..."
> ***
>
> And I think the last paragraph is very contundent on what pop3 was
> designed for.
>    

Wikipedia is not a definitive source for such things.  Now if you can 
point to statements
by John Myers or Marshall Rose, say in the archives of an ietf mailing 
list, that would
be a more definitive statement of the authors' intent.


-- 
In theory, there is no difference between theory and practice.
In<fnord>  practice, there is.   .... Yogi Berra



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