[Dovecot] LDA vs. LMTP

[Steffen Kaiser]

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On Fri, 26 Jul 2013, Martin Burgraf wrote:

> I'm using Dovecot together with Postfix; as I understand it, there are two ways to transfer the mail from Postfix to Dovecot.
> 1.) by using LDA with mailbox_command = /usr/libexec/dovecot/dovecot-lda -f "$SENDER" -a "$RECIPIENT"
> 2.) by using LMTP with mailbox_transport = lmtp:unix:private/dovecot-lmtp
>
> (currently using number 1)
> I'm interessted in the differences and the advantages/disadvantages of each of those solutions.
>
> According to http://wiki2.dovecot.org/LDA the recommended way is to use LMTP, since it's supposed to have a better performance.
> On the other hand, http://wiki2.dovecot.org/LMTP says, that LMTP is a backgound process, while LDA is only called when needed. I've also read, that LDA only uses the users privileges, which both means, that LDA should be better.
> I've also noticed, that LMTP adds an additional Recieved:-Header to the mail.
> Are there any other differences?

LMTP also adds "Delivered-To", unless I'm mistaken.

There is one difference, that pops up on failure: The LDA has the exit 
code only to return success/failure back to the MTA. LMTP uses the same 
mechanisms as SMTP to return success / failure incl. descriptive 
information.

There is another difference, if you need additional hacking: With the 
LDA-method you can put a wrapper script between MTA and MDA, in order to 
alter the message, recipient, just log something, ... . Actually that 
self-made wrapper script [and I really mean script in the sense of bash, 
perl, python, C, ruby, ...] can control the delivery fully. That would be 
more sophisticated to do with LMTP.

- -- 
Steffen Kaiser
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