To remove the bounce status of a contact, go into the Contacts overview, and select one or more contacts with a hard bounce status.
Then, click on "Remove status" and choose "Remove bounce status":
The contact will have its hard bounce status removed and will be able to receive email campaigns again.
Warning
Do this only if you are certain that the email address exists and is able to receive email! Sending to invalid or non-existing email addresses will impact your bounce rate. A too high bounce rate may lead to the email domain being disabled entirely.
For this reason, it's necessary to audit your hard bounces regularly and check them one-by-one to see if the email address is valid and legitimate. Do not remove the hard bounce flag if this is not the case.