Outlook Autodiscovery Issues

Hello! Anyone else having issues with Outlook Autodiscovery (for current versions, Outlook New for Windows, Outlook for Mac and Outlook for Mobile)? Axigens documentation for this isn’t exactly clear or up to date, and for Outlook only references 2016 which is quite old now. Outlook seems to use now use autodiscover.json and autodiscover.xml but with additional queries as a post request and things know (honestly not sure, Microsofts docs aren’t exactly clear on this).

That said, watching everything.log, I can see basic autodiscover.xml attempts from Microsoft are being given a 501 Not Impemented.

Can anyone clarify the required setup subdomains/DNS Records for Autodiscovery to work with Outlook nowadays? I’ve gotten it working before - does the AutodiscoveryParams have to use subdomains, i.e autodiscover.axigentesting.xyz or imap.axigentesting.xyz - or can I just use the root domain?

2025-08-02 08:05:08 +0000 08 vultr WEBMAIL:0000007D: [45.77.51.103:443] connection accepted from [52.125.128.12:4356]
2025-08-02 08:05:08 +0000 08 vultr WEBMAIL:0000007D: connection closed with [52.125.128.12:4356]
2025-08-02 08:05:08 +0000 08 vultr WEBMAIL:0000007E: [45.77.51.103:443] connection accepted from [52.125.128.12:4367]
2025-08-02 08:05:08 +0000 08 vultr WEBMAIL:0000007E: connection closed with [52.125.128.12:4367]
2025-08-02 08:05:08 +0000 08 vultr WEBMAIL:0000007F: [45.77.51.103:443] connection accepted from [52.125.128.12:4363]
2025-08-02 08:05:08 +0000 08 vultr WEBMAIL:0000007F: connection closed with [52.125.128.12:4363]
2025-08-02 08:05:08 +0000 08 vultr WEBMAIL:00000080: [45.77.51.103:443] connection accepted from [52.125.128.12:4354]
2025-08-02 08:05:08 +0000 08 vultr WEBMAIL:00000080: connection closed with [52.125.128.12:4354]
2025-08-02 08:05:09 +0000 08 vultr WEBMAIL:00000081: [45.77.51.103:80] connection accepted from [52.125.128.12:4365]
2025-08-02 08:05:09 +0000 08 vultr WEBMAIL:00000081: <> GET /autodiscover/autodiscover.xml HTTP/1.1 u= code=501 time=0
2025-08-02 08:05:09 +0000 08 vultr WEBMAIL:00000081: connection closed with [52.125.128.12:4365]
2025-08-02 08:05:09 +0000 08 vultr WEBMAIL:00000082: [45.77.51.103:80] connection accepted from [52.125.128.12:4358]
2025-08-02 08:05:09 +0000 08 vultr WEBMAIL:00000082: <> GET /autodiscover/autodiscover.xml HTTP/1.1 u= code=501 time=0
2025-08-02 08:05:09 +0000 08 vultr WEBMAIL:00000082: connection closed with [52.125.128.12:4358]

Could it be that it only works on TLS 1.0?
https://www.axigen.com/documentation/auto-discovery-for-em-client-via-imap-pop3-caldav-carddav-p49120006

Autodiscovery is always a fun game to get right. As you say, there’s lots of confusing and contradictory documentation out there. What I do is use Microsoft’s online checker to make sure my server replies as expected.

The complete DNS settings I have settled on (for a multi-domain server) are:

Example1.com = default domain:
@ MX 10 mail.example1.com.
_autodiscover._tcp SRV 5 0 443 mail.example1.com.
_caldav._tcp SRV 10 0 80 mail.example1.com.
_caldavs._tcp SRV 5 0 443 mail.example1.com.
_carddav._tcp SRV 10 0 80 mail.example1.com.
_carddavs._tcp SRV 5 0 443 mail.example1.com.
_imap._tcp SRV 10 0 143 mail.example1.com.
_imaps._tcp SRV 5 0 993 mail.example1.com.
_pop3._tcp SRV 10 0 110 mail.example1.com.
_pop3s._tcp SRV 5 0 995 mail.example1.com.
_submission._tcp SRV 10 0 587 mail.example1.com.
webmail A 0.0.0.0
mail A 0.0.0.0

Example2.net = secondary domain hosted on example1.com:
@ MX 10 mail.example1.com.
_autodiscover._tcp SRV 5 0 443 mail.example1.com.
_caldav._tcp SRV 10 0 80 webmail.example2.net.
_caldavs._tcp SRV 5 0 443 webmail.example2.net.
_carddav._tcp SRV 10 0 80 webmail.example2.net.
_carddavs._tcp SRV 5 0 443 webmail.example2.net.
_imap._tcp SRV 10 0 143 mail.example1.com.
_imaps._tcp SRV 5 0 993 mail.example1.com.
_pop3._tcp SRV 10 0 110 mail.example1.com.
_pop3s._tcp SRV 5 0 995 mail.example1.com.
_submission._tcp SRV 10 0 587 mail.example1.com.
webmail A 0.0.0.0

… to be honest, it doesn’t seem to matter what the _caldav etc. entries point to “mail.” or “webmail.” - both seem to work.

The Microsoft ActiveSync test tool I referred to earlier is: Microsoft Remote Connectivity Analyzer

To add to the above - make sure your certificate for mail.example1.com has SAN entries for all your “autodiscover.example1.com” “autodiscover.example2.net” etc. domain entries.

The certificate is key here!