If your emails are one-time only are unsubscribe links a requirement?

The Spam tests seems to show that it's a low priority issue but doesn't really go into detail.

I ask as the campaign we're running is ad-hoc and automatically sends a a one-off email on request from a user, without any follow-ups of any sort.

As we didn't want to jump through the hoops of GDPR for a one-off campaign, all email addresses are removed from the database immediately after sending.