You can set it to any other time or deselect it. see image

The issue is that, every 5 minutes, the current incomplete draft message is being erroneously sent to recipients, instead of being correctly stored (unsent) in the Drafts folder as an interim saved draft. Changing from host folder to local folder as the Drafts folder location does not change behavior.

Just to clarify, you have set drafts to draftfolder and not to outbox? (account settings / copies & folders / drafts and templates ) and in config ( Option / advanced/general/ config editor ( a button)): mail.default_sendlater_uri points to the right mailbox I save my drafts in local folders so ity looks like this: mailbox://nobody@Local%20Folders/Unsent%20Messages

A workaround until we find whats wrong could be to address it to yourself until your done. then change recipients. How does offline works?