How do I search for a specific contact in order to change their e-mail address?

[TonyP3735]

See above...

[William_A]

Hello @TonyP3735 ,

You can search based on various contact fields while looking at either a specific list or the overall Contacts subtab. To edit a contact, simply click on them to open their contact card.

If the contact's email address has been unusbscribed and resubscribed before, or if there's been anything that's forced its permissions to be locked-in for Compliance, you likely won't be able to update it. In this case, you'll need to add the new email address as a wholly new contact.