SendAsDeniedException

Hello there,

I get this error when not-logged on users want to send a contact form 7 form. How can I fix this? It looks like a API error.

[25-Jun-2020 20:45:19 UTC] ERROR PostmanWpMail: Exception code=554 message=5.2.0 STOREDRV.Submission.Exception:SendAsDeniedException.MapiExceptionSendAsDenied; Failed to process message due to a permanent exception with message Cannot submit message. 0.35250:0A007684, 1.36674:0A000000, 1.61250:00000000, 1.45378:02000000, 1.44866:5C280000, 1.36674:0E000000, 1.61250:00000000, 1.45378:61280000, 1.44866:44010000, 16.55847:75130000, 17.43559:0000000024020000000000000000000000000000, 20.52176:140F258C1B00103100000000, 20.50032:140F258C8B17000000000000, 0.35180:140F258C, 255.23226:0A007984, 255.27962:0A000000, 255.27962:0E000000, 255.31418:0A007A84, 0.35250:1F001432, 1.36674:0A000000, 1.61250:00000000, 1.45378:02000000, 1.44866:3C000000, 1.36674:32000000, 1.61250:00000000, 1.45378:41000000, 1.44866:01000000, 16.55847:A8000000, 17.43559:0000000070030000000000000600000000000000, 20.52176:140F258C1B00101053000000, 20.50032:140F258C8B170000331E0000, 0.35180:58000000, 255.23226:4800D13D, 255.27962:0A000000, 255.27962:32000000, 255.17082:DC040000, 0.27745:3D1E0000, 4.21921:DC040000, 255.279