Hi Felix, Thanks for the report. You’re right: the AUTH=... line in James’s SMTP EHLO response does not conform to RFC 5321. SMTP AUTH mechanisms should be advertised as AUTH OAUTHBEARER XOAUTH2 in this example. AUTH=... is likely an IMAP capability format and does not belong in the SMTP response.
I checked the James code history. This behavior has existed since at least 2015, likely a stale bug. It seems it only happens for SMTP though, other protocols are fine. A PR would be very welcome. Thanks for offering to fix it. Best regards, Quan On Mon, Sep 21, 2026 at 9:11 PM Felix Auringer <[email protected]> wrote: > Hey, > > I noticed that James sends its authentication mechanisms for SMTP twice, > once with a space and once with an equal sign: > > 220 Hello from <my domain> > ehlo example.internal > 250-<my domain> Hello example.internal [84.186.194.95]) > 250-AUTH OAUTHBEARER XOAUTH2 > 250-AUTH=OAUTHBEARER XOAUTH2 > 250-PIPELINING > 250-ENHANCEDSTATUSCODES > 250 8BITMIME > ``` > > As far as I understand, this is not compliant with the RFC ( > https://www.rfc-editor.org/info/rfc5321/#section-4.1.1.1): > > ehlo-ok-rsp = ( "250" SP Domain [ SP ehlo-greet ] CRLF ) > / ( "250-" Domain [ SP ehlo-greet ] CRLF > *( "250-" ehlo-line CRLF ) > "250" SP ehlo-line CRLF ) > ehlo-line = ehlo-keyword *( SP ehlo-param ) > > The only character allowed to follow directly after the ehlo keyword > (AUTH) is a space. > I am also not entirely sure whether sending the same ehlo keyword twice is > allowed. > We use one client that can not handle the line with the equal sign: > https://github.com/simonrob/email-oauth2-proxy/blob/6599460ef7ea99a0ca9515d2457d1666cccb965a/emailproxy.py#L2334 > (admittedly, this is an unusual one). > But other large email servers like Google or Microsoft only announce their > authentication mechanisms once and without the equal sign. > > Is there a reason why you deviate from the standard? > I would be open to submit a PR making James compliant to RFC 5321. > > Best regards, > Felix > --- > Gesellschaft für interkulturelles > Zusammenleben gGmbH (GIZ) > Felix Auringer > IT > Reformationsplatz 2 > 13597 Berlin > > Tel: 030/513 0100 00; Fax: 030/513 0100 09 > www.giz.berlin; [email protected] > > Amtsgericht Charlottenburg HRB 200872 B > Geschäftsführerin: Dr. Britta Marschke > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [email protected] > For additional commands, e-mail: [email protected] > >
