This is likely related more to the configuration of the email server. Outlook is very picky, and as far as I know, checks the headers for all of the following:
Tue, Nov 2
Aug 19 2021
To be fair, I'm almost certainly not going to install yet another client just for this community chat. (I know I'm not alone in this, projecting forward into the project's future.) Matrix + IRC with bridges to the other protocols seems the way to go. (I'm usually on IRC...albeit, not much this month because my plate's full.)
Aug 11 2021
Any user should be able to sign the doc at L1 Phorge Vision Statement - did you try it and got an error?