How do I send a contact plain text emails only?

You can set the delivery format to plain text (rather than the default HTML):

1. Click Contacts in the main navigation menu.
2. Locate the contact by entering a full or partial name or email address in the Search box.
3. Click the down arrow next to the contact, and select Edit.
4. Go to the Other Details tab, and under "Email format" select plain text.
5. Click Update and Close when you have finished making changes.