Message Center Error Help

Hi folks,

Looking for some advise if possible please.

When replying to a message via the message center after submitting my reply I was presented with the following error message.

"ErrorMessage could not be sent.

Mailer Error: SMTP Error: data not accepted.SMTP server error: DATA END command failed Detail: STOREDRV.Submission.Exception:SendAsDeniedException.MapiExceptionSendAsDenied; Failed to process message due to a permanent exception with message Cannot submit message. 0.35250:392C0000, 1.36674:0A000000, 1.61250:00000000, 1.45378:02000000, 1.44866:38390000, 1.36674:0E000000, 1.61250:00000000, 1.45378:3D390000, 1.44866:44010000, 16.55847:C01B0000, 17.43559:0000000024020000000000000000000000000000, 20.52176:140F908C1700F01F00000000, 20.50032:140F908C8717F01F00000000, 0.35180:140F908C, 255.23226:AF2C SMTP code: 554 Additional SMTP info: 5.2.0"

Any help or guidance would be hugely appreciated. Our email settings seem to work for all other aspects CS-Cart.

Many thanks