Why uw.edu not accepted my signed email?

[Daniel Tameling]

On Tue, Nov 16, 2021 at 04:36:43PM -0500, Andrew D. Arenson wrote:
> 	I receive email using IMAP via a davmail process that in turn interacts with Indiana University's Office 365 Exchange instance.

If you use davmail, you don't have to use TLS for sendmail: "SSL is not necessary when DavMail is used in workstation mode, as communication between clients and DavMail remain local. However, in server (shared) mode e.g. with a smartphone connecting to DavMail over the internet, you should make sure encryption is enabled." (http://davmail.sourceforge.net/sslsetup.html)

If you want to use TLS, the link contains also information on how to set that up.

The TLS connection between davmail and the Exchange server is taken care of by davmail itself and it seems to be working in your setup as you can read emails through davmail.

Personally I use msmtp instead of sendmail. I'm currently not at my work notebook but a quick google search turned up this with a .msmtprc that looks reasonable: https://cstan.io/?p=8790&lang=en

It shouldn't be too much work to set that up in case you want to try it in order to be sure your setup is otherwise correct.

-- 
Best regards,
Daniel