@MBeat33 has pointed out that we put email address on hold in Civi based on Acoustic events that might in some cases be transitional - this seems to particularly affect comcast
A specific example is 76161471732 who has been put on hold in CiviCRM due to a 'Reply Email Block' activity in Acoustic on 2024-11-21 09:47:49 - but who is not showing as opted out in Acoustic (although they might be on the master suppression list?)
https://civicrm.wikimedia.org/civicrm/contact/view?reset=1&cid=5530613&selectedChild=omnimail