Exim4 failts to use smtp.office365.com as its smarthost

[Sébastien Hinderer]

Dear all,

Here is the relevant excerpt from mainlog:

2023-08-04 07:19:33 1qRnDp-002mcZ-0B <= mail at domain.org U=user P=local S=470 id=ZMyKZdvYD7a0zP8z at om.localdomain
2023-08-04 07:19:33 1qRnDp-002mcZ-0B H=CDG-efz.ms-acdc.office.com [2603:1026:c0a:1862::2]: CDG-efz.ms-acdc.office.com [2603:1026:c0a:1862::2]: Network is unreachable
2023-08-04 07:19:33 1qRnDp-002mcZ-0B H=CDG-efz.ms-acdc.office.com [2603:1026:c0a:8e8::2]: CDG-efz.ms-acdc.office.com [2603:1026:c0a:8e8::2]: Network is unreachable
2023-08-04 07:19:33 1qRnDp-002mcZ-0B H=CDG-efz.ms-acdc.office.com [2603:1026:100:15::2]: CDG-efz.ms-acdc.office.com [2603:1026:100:15::2]: Network is unreachable
2023-08-04 07:19:33 1qRnDp-002mcZ-0B H=CDG-efz.ms-acdc.office.com [2603:1026:c0a:8f3::2]: CDG-efz.ms-acdc.office.com [2603:1026:c0a:8f3::2]: Network is unreachable
2023-08-04 07:19:38 1qRnDp-002mcZ-0B H=CDG-efz.ms-acdc.office.com [52.98.228.34] TLS error on connection (recv): The TLS connection was non-properly terminated.
2023-08-04 07:19:38 1qRnDp-002mcZ-0B H=CDG-efz.ms-acdc.office.com [52.98.228.34] TLS error on connection (recv): The specified session has been invalidated for some reason.
2023-08-04 07:19:38 1qRnDp-002mcZ-0B H=CDG-efz.ms-acdc.office.com [52.98.228.34] TLS error on connection (recv): The specified session has been invalidated for some reason.

Is this fixable and, if yes, does anybody here knowhow please, or should
I use an upstream mailing list?

Any help warmly appreciated because I need to interact with Teams group
from an address which is managed by office365 and if I try to send an
email  which does have this address in its From  headers but through an
other smarthost, it fails. So I am stuck at the moment.

Cheers,

Seb.