LenoxSoft sends a list email to the "2019 Tradeshow" list, and does not use a...

The prospect already received the email already received another Marketing Cloud Account Engagement email within the past business day, based on the account's business hours.

The Dedicated IP address was not warmed up appropriately before the email was scheduled.

The prospect was no longer a member of the "2019 Tradeshow" list used for the email send.

A second prospect with the same email address received the email under "allow multiple prospects with the same email address.'