Hi Stan, hi all,
I'm having the same issue. Guess I tried most of the settings. Talked to the guys at ionos. The closest I got was by ESMTP and TLS v1.2exp:
[01] 4/15 23:59:16 ~ Opening connection for delivery...
[01] 4/15 23:59:16 ~ Connecting to smtp.exchange2019.ionos.de Port:587...