Online Qt installer for Windows is blocked by Symantec Endpoint Protection

It seems Symantec Endpoint Protection is flagging the current version of our online Windows installer (qt-unified-windows-x86-3.1.0-online.exe) as a low-reputation file and blocking access to it to prevent a security risk, which may scare away a few customers. Reputation-based checking uses crowdsourcing info, so it may be because the file is new. Microsoft SmartScreen uses a similar reputation-based checking as well (which does not seem to be flagging it). Resolution of this issue would require finding out if there is a way to prevent this kind of scary warning, like signing the exe with a higher-class certificate, or requesting white-listing / reporting a false positive to Symantec (which may need to be done for every new release).