Office365 Outlook "target principal name is incorrect" error with multi-domain cert

[Bruce5051]

@Bruce5051

But all 3 are sending the Self-signed ISRG Root X1 (RSA 4096, O = Internet Security Research Group, CN = ISRG Root X1) which they should not be doing.

Here are 3 more links on Chains:

Verifying a certificate

…

Long (default) and Short (alternate) Certificate Chains Explained

I…

Choice of default long chain vs short chain

I…