Hi, I have similar issue but none of the workarounds worked for me. This is the log I receive when I try to send emails on behalf of my business email account:
Your message did not reach some or all of the intended recipients. Subject: TEST Sent: 20/08/2024 17:35 The following recipient(s) cannot be reached: 'pc_******@hotmail.co.uk' on 20/08/2024 17:35 This message could not be sent. You do not have the permission to send the message on behalf of the specified user. __________________________________________________ Diagnostic information for administrators: __________________________________________________ Error is [0x80070005-0x000004dc-0x00000524]. Exchange response headers: request-id: fb845061-c9c2-23b3-abcb-fdafd41d760e X-ServerApplication: Exchange/15.20.7875.019 X-FEServer: LO4P123CA0097 X-BEServer: LO2P265MB4487 X-CalculatedBETarget: LO2P265MB4487.GBRP265.PROD.OUTLOOK.COM X-RequestId: {0A878D8E-6726-47D4-960F-37CB62B720A8}:38 X-ClientInfo: {C75C9679-5F41-4BCB-AF5A-B96B1183B820}:222960015 X-ElapsedTime: 920 X-BackEndHttpStatus: 200 X-ResponseCode: 0 X-DiagInfo: LO2P265MB4487 X-RequestType: Execute __________________________________________________ ROPs Summary: 0: ropSetProps (10) Processed(1) Completed(0) ROP result: 0 Response codes: 0 1: ropFlushRecipients (14) Processed(1) Completed(0) ROP result: 0 Response codes: 0 2: ropSetProps (10) Processed(1) Completed(0) ROP result: 0 Response codes: 0 3: ropTransportSend (74) Processed(1) Completed(0) ROP result: 0 Response codes: 1244 __________________________________________________ Response Exceptions: ROP Index: 3 ROP Associated: ropTransportSend (74) Microsoft.Exchange.Data.Storage.SendAsDeniedException: Can't send message. ---> Microsoft.Mapi.MapiExceptionSendAsDenied: MapiExceptionSendAsDenied: TransportSend operation has failed (hr=0x80070005, ec=1244) 1.84300:0B000000, 1.84300:0A000000, 1.84300:0A000000, 1.84300:0E000000, 1.84300:4A000000, 1.116652:920C0000, 1.81836:3C020000, 0.117068:2C000000, 1.79180:0B000000, 1.79180:0A000000, 1.79180:0A000000, 1.79180:0E000000, 1.79180:4A000000, 1.79180:FA000000, 0.73100:15000000, 0.38698:05000780, 1.41134:87000000, 0.29756:87000000, 1.104236:00000000, 1.87852:00000000, 1.120620:00000000, 1.75564:00000000, 5.108332:000000004D6F4D5400000100, 6.64024:1A0104800300140E00000000, 4.41064:1A010480, 1.104236:00000000, 1.87852:00000000, 1.120620:00000000, 1.75564:00000000, 5.108332:000000004D6F4D54003B3B00, 6.45653:050007804000073000000000, 4.41064:05000780, 1.104236:00000000, 1.87852:00000000, 1.120620:00000000, 1.75564:00000000, 5.108332:000000004D6F4D5400000780, 6.64024:1A0104800300161000000000, 4.41064:1A010480, 1.104236:00000000, 1.87852:00000000, 1.120620:00000000, 1.75564:00000000, 5.108332:000000004D6F4D5400000780, 6.45653:050007804000083000000000, 4.41064:05000780, 1.104236:00000000, 1.87852:00000000, 1.120620:00000000, 1.75564:00000000, 5.108332:000000004D6F4D5400000780, 6.45653:050007801F00FA3F00000000, 4.41064:05000780, 1.104236:00000000, 1.87852:00000000, 1.120620:00000000, 1.75564:00000000, 5.108332:000000004D6F4D5400000780, 6.64024:1A0104800201E26500000000, 4.41064:1A010480, 1.104236:00000000, 1.87852:00000000, 1.120620:00000000, 1.75564:00000000, 5.108332:000000004D6F4D5400000000, 6.64024:1A0104800201E36500000000, 4.41064:1A010480, 1.41134:87000000, 6.46872:050007800201F90F00000000, 4.55098:05000780, 1.41134:47000000, 0.37692:00000000, 0.37948:00000000, 5.33852:00000000534D545000000000, 4.56248:DC040000, 7.40748:010000000000010B00000000, 7.57132:000000000000000000000000, 4.39640:DC040000, 1.63016:4A000000, 8.45434:FE7F0300BF84F5A4000000000000000000000000, 1.46798:13000000, 5.10786:0000000031352E32302E373837352E3031393A4C4F32503236354D42343438373A33383866386361652D333432352D343330332D383230352D3737393933633132663439383A36313439323A2E4E455420382E302E37003000000000, 7.51330:106A480436C1DC0800000000, 0.39570:05000780, 1.55954:0B000000, 0.40818:07000000, 1.33010:0B000000, 2.54258:00000000, 0.59634:00000000, 1.56562:00000000, 1.33010:0B000000, 2.54258:00000000, 0.59634:00000000, 1.56562:00000000, 1.55954:0A000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:07000000, 1.56562:00000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:00000000, 1.56562:00000000, 1.55954:0A000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:15000000, 1.56562:00000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:00000000, 1.56562:00000000, 1.64146:0E000000, 1.33010:0E000000, 2.54258:00000000, 1.33010:0E000000, 2.54258:00000000, 1.64146:4A000000, 1.33010:4A000000, 2.54258:DC040000, 1.33010:4A000000, 2.54258:DC040000, 0.79500:80060400, 0.100684:01000000, 4.108172:DC040000, 1.52466:02000000, 1.52466:02000000, 1.42738:0B000000, 0.37698:01000000, 1.42738:0B000000, 0.37698:01000000, 0.60402:00000000 at Microsoft.Mapi.Managed.MapiExceptionHelper.ThrowIfError(LID lid, IHandle objectHandle, String message) at Microsoft.Mapi.Managed.MapiMessage.Implement_TransportSendMessage(PropValue[]& propsToReturn) at Microsoft.Mapi.Managed.MapiMessage.TransportSendMessage(PropValue[]& propsToReturn) at Microsoft.Exchange.Data.StoreObjects.MapiAccessorExtensionMethods.TransportSendMessage(IStoreSession storeSession, Object mapiObject, ExTimeZone timezone, PropValue[]& mapiPropValues) --- End of inner exception stack trace --- at Microsoft.Exchange.Data.StoreObjects.MapiAccessorExtensionMethods.TransportSendMessage(IStoreSession storeSession, Object mapiObject, ExTimeZone timezone, PropValue[]& mapiPropValues) at Microsoft.Exchange.Data.Storage.CoreItem.TransportSend(PropertyDefinition[]& properties, Object[]& values) at Microsoft.Exchange.Data.StoreObjects.ProxyCoreItem.TransportSend(PropertyDefinition[]& properties, Object[]& va Transport-Send failed: failure enum(25), HResult(0x00000000), EC(1244). Transport-Send failed: failure enum(22), HResult(0x00000000), EC(1244). Submit-Message failed: message id(1), failure enum(13), HResult(0x80070005), EC(1244).