TFS issue modification error for external email account

[danseo-reisys]

Hello,
New TFS issue gets created fine when our client sends an email to our TFS service email address.
but anytime our client replies to the email thread, this mail2bug shows following error and does not modify existing TFS issue.
Anytime someone in our email group replies, TFS issue gets updated fine. This behavior persists for all external client email address.

Can you please make some recommendation?

2022-01-06 11:50:56,913 [3] INFO TfsEmailService.MessageProcessingStrategies.SimpleBugStrategy [(null)] - Modifying work item 191706 subject: RE: EXTERNAL: test
2022-01-06 11:50:56,916 [3] INFO TfsEmailService.MessageProcessingStrategies.NameResolver [(null)] - Resolving name for alias/name larsenp/Peter Larsen
2022-01-06 11:50:56,917 [3] WARN TfsEmailService.MessageProcessingStrategies.SpecialValueResolver [(null)] - Name resolution failed for sender alias 'larsenp'. Returning display name.
2022-01-06 11:50:56,949 [3] WARN TfsEmailService.WorkItemManagement.TFSWorkItemManager [(null)] - 'Peter Larsen' is an invalid value for Changed By. Trying to find approximate value.
2022-01-06 11:50:56,952 [3] INFO TfsEmailService.WorkItemManagement.TFSWorkItemManager [(null)] - Approximate value is
2022-01-06 11:50:57,217 [3] ERROR TfsEmailService.Mail2BugEngine [(null)] - Error processing message
Microsoft.TeamFoundation.WorkItemTracking.Client.UnexpectedErrorException: There is a problem on the server. Contact your Team Foundation Server administrator. ---> System.Web.Services.Protocols.SoapException: Object reference not set to an instance of an object.
at Microsoft.TeamFoundation.WorkItemTracking.Proxy.RetryHandler.HandleSoapException(SoapException se)
at Microsoft.TeamFoundation.WorkItemTracking.Proxy.WorkItemServer.Update(String requestId, XmlElement package, XmlElement& result, MetadataTableHaveEntry[] metadataHave, String& dbStamp, IMetadataRowSets& metadata)
at Microsoft.TeamFoundation.WorkItemTracking.Client.WorkItemStore.SendUpdatePackage(XmlElement package, XmlElement& result, Boolean bulk)
--- End of inner exception stack trace ---
at Microsoft.TeamFoundation.WorkItemTracking.Client.WorkItemStore.SendUpdatePackage(XmlElement package, XmlElement& result, Boolean bulk)
at Microsoft.TeamFoundation.WorkItemTracking.Client.WorkItemStore.SaveWorkItems(WorkItem[] workitems, Boolean bulk, SaveFlags saveFlags)
at Microsoft.TeamFoundation.WorkItemTracking.Client.WorkItem.Save(SaveFlags saveFlags)
at TfsEmailService.WorkItemManagement.TFSWorkItemManager.ValidateAndSaveWorkItem(WorkItem workItem) in C:\gh\TfsEmailService\TfsEmailService\WorkItemManagement\TFSWorkItemManager.cs:line 414
at TfsEmailService.WorkItemManagement.TFSWorkItemManager.ModifyWorkItem(Int32 workItemId, String comment, Dictionary`2 values) in C:\gh\TfsEmailService\TfsEmailService\WorkItemManagement\TFSWorkItemManager.cs:line 321
at TfsEmailService.MessageProcessingStrategies.SimpleBugStrategy.UpdateWorkItem(IIncomingEmailMessage message, Int32 workItemId) in C:\gh\TfsEmailService\TfsEmailService\MessageProcessingStrategies\SimpleBugStrategy.cs:line 178
at TfsEmailService.MessageProcessingStrategies.SimpleBugStrategy.ProcessInboxMessage(IIncomingEmailMessage message) in C:\gh\TfsEmailService\TfsEmailService\MessageProcessingStrategies\SimpleBugStrategy.cs:line 44
at TfsEmailService.Mail2BugEngine.ProcessInboxInternal() in C:\gh\TfsEmailService\TfsEmailService\Mail2BugEngine.cs:line 90

[davisjr]

Looks like it's not able to update the Changed by field since the person is not in your organization. Could you try dropping the default for Changed by in your config so that the updates are marked as done by the account running mail2bug instead of the sender.