So, it would end up looking at values within the arrComplaint array:

Public Sub SendEMail(ByVal rngStart As Excel.Range)

    Dim arrComplaint            As Variant

    arrComplaint = rngStart.Resize(1, 20).Value


    Set OutApp = CreateObject("Outlook.Application")
    Set OutMail = OutApp.CreateItem(0)
 
    On Error Resume Next
    With OutMail
        .To = ""
        .CC = ""
        .BCC = ""
        .Subject = "Complaint ID" & cstr(arrComplaint(1,1))
        .Body = "Complaint ID " & cstr(arrComplaint(1,1)) & " has no progress for 5 days"
        .Display
    End With
    On Error GoTo 0

    With Application
        .EnableEvents = True
        .ScreenUpdating = True
    End With
 
    Set OutMail = Nothing
    Set OutApp = Nothing
    
End Sub
You would change the second 1 to bring up different columns from the database, i.e.:

arrcomplaint(1,8)

would show the department.