What difference does it make that the email is sent after work hours or not? It’ll still be in their inbox the morning after.
Not trying to be facetious here, we have similar laws where I live, and employers respect that.
But all it changes is that you have to do a lot more in the 9 hours a day you’re on duty. The clients’ needs don’t just stop at 17.00. Either I voluntarily work through my lunches and evenings, or I get replaced by someone who does or who can somehow cram 14h of labor in 8h.