Application Control mismatch application

[MosheVan]

Application Control on R80.20 identifies SMTP traffic as VNC Traffic,

VNC is categorized by checkpoint as high risk application and there is a rule to prevent High Risk Applications.

So eventually legitimate SMTP Traffic is blocked.

[PhoneBoy]

There was an issue in recent App Control signatures that flagged this as a false positive. 
Update your signatures to the most recent version and this problem should be resolved.