Greenmail should be disabled by default

[stokito]

Now there is option greenmail.disable and if user forgot to set it to true greenmail will be started.
It looks not good for me because of security and unexpected behavior.
For example dumpster plugin uses option dumbster.enable
Maybe it will be better to deprecate greenmail.disable and introduce greenmail.enable instead?

[github-actions]

This issue looks like it is stale and therefor it is in risk of being closed with no further action.