yes, i have the same thing happening on one of my server. Basically it is related to the dyndns update which maintain the binding between your domain and your ip address automagically.
It’s not really super interesting to explain what’s going on, the bottom line is that the way it works technically is a bit too brutal and we should try to make it a bit cleaner … I’ll end up doing this when I’m fed up receiving those email as well If you want to know more, these issue are related : https://github.com/YunoHost/issues/issues/1300 and https://github.com/YunoHost/issues/issues/843
If you really want, you can manually tweak the cron job such that the dyndns update happens every 20 minutes and not 2 minutes for instance.