Hello Fond Whitefish, thank you for sharing. To better understand what's going on, could you confirm the following? 1) When you send email to several providers, does it always fail with the same recipients or can it happen to anyone (and only one receives it)? 2) Are you sending them as a campaign to a list/group within MailerLite, or as a test/preview shipment to multiple addresses? 3) When sending, is your goal for everyone to receive the exact same email in the same shipment, or for each provider to receive an individual email separately?