On Thu, May 15, 2025 at 06:48:00PM -0400, Wietse Venema via Postfix-users wrote:
> > > I'd have thought it'd at least try, similar to how it does in when
> > > using my sendmail host. My configuration remained the same, except
> > > for changing the host to the machine running postfix instead.
> >
> > It is not reliable or even reasonable to expect a MUA to try
> > authentication only after an attempt to send without authentication
> > fails. Configure your MUA to authenticate by default and your
> > problem should go away.
>
> "But it works with Sendmail...."
Probably only because the MUA was configured and able to authenticate to
the sendmail host, but not to the new Postfix host. Either because the
client authentication settings did not carry over, or because, if the
configured authentication mechanism is actually GSSAPI, perhaps the new
host has no smtp/<fqdn.example>@REALM principal registered with the
relevant KDC.
The RCPT TO response code is I think unlikely to be relevant.
--
Viktor.
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