MAIL FROM AUTH=<> returns 501 Parameter AUTH is not recognised

[ddaymn]

When sending mails using outlook they are rejected

250-AUTH=CRAM-MD5 PLAIN LOGIN ANONYMOUS
250 AUTH CRAM-MD5 PLAIN LOGIN ANONYMOUS
MAIL FROM:outlook_28E0EB1540D65AC3@outlook.com SIZE=13343 AUTH=<>
501 Parameter AUTH is not recognised
QUIT
221 Goodbye

[rnwood]

Hi. Thanks for reporting this. Can you clarify which platform and version of Outlook this behaviour shows up with (or is this from web based outlook.com?). Also what settings do you have for the outgoing mail server authentication. Thanks Rob

…

________________________________ From: ddaymn <notifications@github.com> Sent: Thursday, November 19, 2020 7:54:53 PM To: rnwood/smtp4dev <smtp4dev@noreply.github.com> Cc: Subscribed <subscribed@noreply.github.com> Subject: [rnwood/smtp4dev] 501 Parameter AUTH is not recognised (#565) When sending mails using outlook they are rejected 250-AUTH=CRAM-MD5 PLAIN LOGIN ANONYMOUS 250 AUTH CRAM-MD5 PLAIN LOGIN ANONYMOUS MAIL FROM:outlook_28E0EB1540D65AC3@outlook.com<mailto:outlook_28E0EB1540D65AC3@outlook.com> SIZE=13343 AUTH=<> 501 Parameter AUTH is not recognised QUIT 221 Goodbye — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub<#565>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AAKEGFYOSOQY4Y7KPWTWWCTSQVZY3ANCNFSM4T33HWXA>.

[ddaymn]

It is outlook.com in general. My thought is that it is the empty AUTH<> I see other messages that work but there are values in between the <>. That value above was from the session log in smtp4dev. I do not have SMTP relay enabled.

[rnwood]

I've had a look at web based Outlook (there's several apps branded as this by MS).

Can you confirm you are referring to the app at https://outlook.live.com/ (not the O365 one at outlook.office.com)
and specifically that this can be reproduced using these settings to get it to send outgoing messages via SMTP:

[GeoMaciolek]

I'm happy to work to troubleshoot this - I'm noticing, this seems to occur when we're using Exchange Online mail routing rules to Redirect a message to this server - sending email directly from the same Office/MS 365 Tenant works fine.

Noting in this case - running on Port 25. default settings, and no MX records; mail was sent to an address like user@asubdomain.mypersonaldomain.com.

[GeoMaciolek]

Here's the session log from the session in question!

220 my.public.hostname smtp4dev ready
EHLO NAM11-BN8-obe.outbound.protection.outlook.com
250-Nice to meet you.
250-8BITMIME
250-SIZE
250-SMTPUTF8
250-AUTH=CRAM-MD5 PLAIN LOGIN
250 AUTH CRAM-MD5 PLAIN LOGIN
MAIL FROM:<bouncesEtr+SRS=8Wfmu=OI=outlook.com=my@employer.com> SIZE=41816 AUTH=<>
501 Parameter AUTH is not recognised
QUIT
221 Goodbye