I use a similar nasal spray for allergies (Becodefence). Basically a physical barrier coating the nasal passages. For me and my allergies, it's super effective.
Never thought about using it to block viral infections, but it makes sense: coating the nasal passages with artificial "mucus-like substance" so particles don't reach the membranes. Makes total sense that approach also work for viruses.
A couple of decades ago, I was on a commercial aircraft and sat next to a man who occasionally puffed something into his nostrils. It turned out that he was a researcher at Ft. Detrick, and he explained that keeping your nasal passages moist with saline spray helped to keep out germs. I’ve been using saline sprays ever since!
Not sure its quality, but battling with postfix & dovecot's 20+ years of legacy cruft, I felt compelled many times to just throw them aside and build something like this on first principles - simple single binary mail server with modern protocol support, sans all the archaic UNIX-account timesharing-era sendmail bullshit that still lives on in the mainstays.
Going to have a look at this one, despite now having moderately deep postfix & dovecot knowledge.