Re: Correct value for EHLO when submitting mail

I think as long as you stick to the RFCs, you'll be fine.  There are some
particularly strict MTAs or filters out there that demand the HELO/EHLO
parameter is RFC compliant.  "localhost" or a bare IP address would be
rejected.

SPF would also possibly fail on "localhost", though it would be weird to
check internal IP addresses for SPF compliance.


On Wed, Jan 29, 2014 at 12:08 PM, Jan Kundrát <[email protected]> wrote:

> Hi,
> when a MUA submits e-mail over SMTP, what value shall be used in the
> HELO/EHLO greetings? Shall I just stick with "localhost", or trust the
> OS-reported hostname, if any, or shall I use the IP address of my local
> endpoint?
>
> I see problems with all of these, and apparently Thunderbird went through
> a nice discussion on this matter [1]. I didn't find any answer about that
> in RFC 6409, unfortunately, and RFC 5321's discussion [2] about this topic
> leaves me without a definitive answer, either -- the MUA will have zero
> idea about the "primary host name" and its relation to what OS returns, so
> I'm inclinded to interpret this as a suggestion to use address literals,
> but then I've heard about spam filters penalizing such messages [1]...
>
> What is the current best practice?
>
> With kind regards,
> Jan
>
> [1] https://bugzilla.mozilla.org/show_bug.cgi?id=279525
> [2] http://tools.ietf.org/html/rfc5321#section-4.1.4
>
> --
> Trojitá, a fast Qt IMAP e-mail client -- http://trojita.flaska.net/
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