StrictPacketPasswords (default is "true").
If you want SBBSecho v3 to behave like SBBSecho v2 with regards to packet
passwords for linked-nodes with *no* configured packet password, set this value
to "true" in your sbbsecho.ini file. I don't recommend doing this if you care
about the "security" of your echomail, but some sysops have been bitten by the
strict enforcement of the configured password in SBBSecho v3.

I also fixed some (but not all) of the signed/unsigned value comparison
warnings reported by msvc2013. Hopefully this didn't introduce any stupid bugs.