Russ Allbery wrote:
Hector Santos <hsantos(_at_)santronics(_dot_)com> writes:
2) What about outgoing?
Are MX records considered the solution?
Using GMAIL as an example, I think it only allows IMAP for receiving and
SUBMIT (port 587) for sending. So wouldn't a SRV record be useful for
the case where SMTP is used for outgoing when the incoming uses IMAP?
As a site where, for various load-balancing, administrative, and
configuration complexity reasons, our outgoing mail servers for clients
are entirely distinct from the inbound servers holding the MX records of
the domain, I would love to see a SRV record for clients to locate
outbound SMTP servers.
I missed section 3.1 which offers the _submission._tcp.domain SRV query.
Don't know if that covers, partially or otherwise, the user needs on
The only thing I see is that normally, the posting host can either be
specific (i.e, "smart host") or MX lookup. But I think it is MUA
A quick review of how TBIRD does it for "Create New Account", it will
use the "default" smtp server setup prepared for the account settings.
So the outgoing part is probably best useful when the user is first
installing his/her MUA.
Also, in terms of a "USER" need, the odds are good his ISP is blocking
port 25 for anything other than the ISP email network. So for non ISP
networks, port 587 "SHOULD" be a preferred selection if offered by the
In my experience, and I helped the TBIRD guys get this added, this is
more important in the growing SOHO or wireless home network with
additional user machines are used.
For SMTP receivers who are "strict" with the EHLO domain literal IP
checking, this can be a problem when the MUA uses the user machine IP
and not the NAT or public IP address for the user.
OE does not have this problem because it will use the netbios computer
name. TBIRD will use a bracket IP of the user' machine.
So I had the TBIRD people address this and the final simple/quick
solution was an Advanced Configuration option (rather than add a new
DIALOG) that allows the EHLO string to be defined.
Tools | General | Config Editor
Type the filter
to see all the mail server fields. I don't recall if I had to add te
first time (in the first beta) and its now added automatically, but
there would be fields called
and if defined, it will be used as the override for the SMTP going
transaction EHLO command. Otherwise, it will use the FQDN for a
public address or the private ip address of the user's machine.
For example from my SOHO machine I have my TBIRD
mail.server.server#.hostname fields set using
[public IP address]
Finally, before this feature was added to TBIRD, because I was using a
SUBMIT server it may have a tight EHLO checking. I proposed to
Klensin and Gellens (RFC 4409) that they consider adding some notes
for relaxing EHLO IP literal checking because SUBMIT requires
authentication anyway which is handled after the EHLO state.
So for our WCSMTP software, we added an option (enabled by default) to
skip EHLO checking for PORT 587 connections based on the idea that
authentication is required anyway, not an option like in public port
25. That was our solution before the TBIRD changes were made.