How can I send emails from outlook to SharePoint Security Groups.
If the SharePoint groups are using AD Security groups, then you can simply send an email to that AD alias from Outlook directly.
If you have individul users within a SharePoint group, you can navigate to the group via Site Settings, People and Groups. From there, tick the little box to select all users and select Actions, Email Users. This will open an Outlook email message and you can construct your message and send it.