[exim] syscall: Connection reset by peer (outlook.com)

Hello,
I'm getting lots of these in exim log:
2021-02-25 04:31:15.790 [19189] SSL_write: (from
mail-pu1apc01hn2214.outbound.protection.outlook.com (APC01-PU1-
obe.outbound.protection.outlook.com) [52.100.183.214]:42879) syscall:
Connection reset by peer

Only a couple are not from outlook.com, so mostly a problem with
outlook.com servers? I am not sure if they find something they don't
like about my TLS and decide to disconnect?

I also get plenty of successful mail from outlook.com so its confusing.
But some remote sender using microsoft reported getting mail returned
due to expired retries/unable to connect.

Can anyone help to understand this more?