If you have the web site for domain.com hosted elsewhere (not on mailinabox) then SSL will NOT work for that domain on mailinabox.
SSL is for web only in your case since mail for domain.com would still be going through box.domain.com.
If you have the web site for domain.com hosted elsewhere (not on mailinabox) then SSL will NOT work for that domain on mailinabox.
SSL is for web only in your case since mail for domain.com would still be going through box.domain.com.