Maybe I’m wrong but the PTR of the IP seems to be in a spam blacklist:

https://apility.io/search?q=infoteam.ch

https://apility.io/search?q=80.74.143.113

https://apility.io/search?q=dynco.ch

This thing happens sometimes, specially if you use a shared hosting. Recently using a well known cloud provider the Public IP address assigned was in a spam blacklist! It’s a good idea to have a look at your IP and domains frequently.

(Disclaimer: I’m the founder of the tool used for the lookup in the blacklists)