If you want to make sure your emails in SeaMonkey are sent/received via secure protocol - set up the following security options:
1. Server Settings
Go to Edit drop-down -> Mail & Newsgroups Account Settings and for your account select SSL secure connection at Server Settings. Press OK to save this option.
2. Outgoing Server settings
Open Outgoing Server (SMTP) and edit your server settings: select SSL secure connection and press OK to save this option.
