Hi Katie! welcome to the community.  This is a great question.  You can send transactional emails to subscribers even if they are suppressed:

Even customers that are suppressed receive transactional emails; the only exceptions are if the suppression reason is due to an email bouncing too many times, the email was invalid, or the customer previously marked a message as spam.

You’ll need to set up your emails and then contact the Customer Success team.  Here’s an article that explains it further:

https://help.klaviyo.com/hc/en-us/articles/360003165732-Guide-to-Using-Flows-to-Send-Transactional-Emails

Hey @Katie M.,

@Mailbox Manny is spot on!

Adding to their point, because transactional emails have the capability of reaching even suppressed profiles with informative emails, they would need to be reviewed and approved by our Klaviyo team members to be marked as transactional. After building your flow and the flow’s email content out, you’ll want to contact our Customer Success team  while using the subject line "Transactional Email Request" so that the request will reach the appropriate team for review. In addition, you’ll also want to include the following details to your request:

• URL link(s) to the flow(s)
• Flow name(s)
• Subject line of the email(s) that are transactional

I hope this helps!

David