Email - no Sender Account info

We receive emails using a Queue email address. It's the Contacts that are associated with Accounts on CRM Online 2016 that send those emails. However, when searching in Advance Find, most of those emails don't have the Sender Account (field is blank) even though the Sender field has the Contact value.

Screenshots below:

Error Details:

Plugin Trace:

[Microsoft.Xrm.Sdk.Workflow: Microsoft.Xrm.Sdk.Workflow.Activities.CreateEntity]
[CreateStep6]

Error Message:

Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=8.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: You should specify a parent contact or account.Detail:
<OrganizationServiceFault xmlns:i="www.w3.org/.../XMLSchema-instance" xmlns="schemas.microsoft.com/.../Contracts">
<ErrorCode>-2147204080</ErrorCode>
<ErrorDetails xmlns:d2p1="schemas.datacontract.org/.../System.Collections.Generic" />
<Message>You should specify a parent contact or account.</Message>
<Timestamp>2016-05-25T09:35:52.9218457Z</Timestamp>
<InnerFault>
<ErrorCode>-2147204080</ErrorCode>
<ErrorDetails xmlns:d3p1="schemas.datacontract.org/.../System.Collections.Generic" />
<Message>You should specify a parent contact or account.</Message>
<Timestamp>2016-05-25T09:35:52.9218457Z</Timestamp>
<InnerFault i:nil="true" />
<TraceText i:nil="true" />
</InnerFault>
<TraceText>[Microsoft.Xrm.Sdk.Workflow: Microsoft.Xrm.Sdk.Workflow.Activities.CreateEntity]
[CreateStep6]
</TraceText>
</OrganizationServiceFault>
at Microsoft.Crm.Workflow.Services.CreateActivityService.Execute(ActivityContext executionContext, CreateEntity createEntity)
at System.Activities.CodeActivity.InternalExecute(ActivityInstance instance, ActivityExecutor executor, BookmarkManager bookmarkManager)
at System.Activities.Runtime.ActivityExecutor.ExecuteActivityWorkItem.ExecuteBody(ActivityExecutor executor, BookmarkManager bookmarkManager, Location resultLocation)