In recent years I have tried several email access checkers but nothing for free has worked better than this, the only one who doesn't skip hits.
It also works very well with shared proxies (I personally use it with @Michigaun proxies)
The software seems clean, I use it without VM but if you have any doubt, the choice is yours!
Download:
Virustotal:
https://www.virustotal.com/gui/file/e436924a2fac62b5df8e77b588ce8e3f8c23075e1367c6c53fbca70ff3107e42/detection
Don't Leech