You can try to run netstat or tcpdump -w file.pcap, then copy the .pcap to your machine and open it with wireshark to see what is going on.
It could be that it is simply incoming packets from the internet, e.g. bots scanning the ports.
Looking at Problem installing chat relay [certificate for shared IPv4 address space] - #3 by broncheolus, you have opened port 22 to the outside internet. Probably better close it and only SSH from your local network if you can. Also make sure to use key authentication on SSH and disable password authentication in /etc/ssh/sshd_config
Otherwise it is constantly flickering because of the bots trying to bruteforce the SSH password.
Chatmail relay itself is not sending anything other than outgoing mails normally.