LMTP - big advantages?

[Smebobo]

Hi there,

I'm trying to figure out what the benefit of using LMTP between my front end mail relay and Zimbra would bring. Maybe I don't understand LMTP well enough, but as I see it there aren't any major advantages.. Can someone correct me?

Thanks!

-Satri

[djve]

I don't have the original posts but I have some notes from the last time I searched the web on this. You may want to dig into the RFC for technical details. Maybe someone from Zimbra will have a more succinct explanation.

In LMTP when there are more than one recipient of the message, the LMTP server can report to client one response code for each recipient. With SMTP only one SMTP response has to describe the complete situation for all recipients.

Consider a case of three recipients and a virus or spam message:
- one recipient is a normal user, virus needs to be blocked;
- one is a virus lover, mail gets successfully delivered to him;
- the third one does not exist and next-hop MTA rejects it;

This clearly requires different SMTP response codes. With LMTP three response codes get returned to the MTA. With (E)SMTP it is only posible to describe the situation by:
- returning 250 success response code;
- generating proper DSN (delivery status notifications) by amavisd-new
itself, as required by standards.

And from somewhere else I don't have noted:

LMTP makes it possible to synchronize the data between a serveur smtp and few mailbox of the users, especially if mailbox them are on a distant machine.

LMTP speaks a protocol similar to smtp which is optimized for the delivery
with the server of mailbox such Cyrus. The advantage of this configuration
is that a Postfix machine can supply several server of mailbox via LMTP. The
opposite is true also: a mailbox server can be supplied via LMTP by multiple
Postfix machines.

Posftix and cyrus use LMTP.

Hope this helps.