Email Campaigns cannot be deleted, only archived. You can archive email campaigns that you are no longer using.
If later you need to use an archived email campaign you can UnArchive it.

Archived Email Campaigns can not be Edited or Configured unless you UnArchive them.

When a email campaign is archived, any Auto Sender or Triggered Emails will be turned off.

To archive an email campaign:

1. Go to Email Campaigns on the main navigation menu.
2. Under one of your existing email campaigns select the Configure icon > Archive

To unarchive an email campaign:

1. Go to Email Campaigns > Archived Email Campaigns on the main navigation menu.
2. Under one of your existing archived email campaigns select the Configure icon > UnArchive