How to understand the meaning of an email header meta data

[iMore Question]

I am trying to understand what the following email message header can tell me. Does it represent two different mail clients? Two different phones? Thanks for your help.
X-Mailer: iPhone Mail (5G77)
Apple-Mail-2--212350786
Mime-Version: 1.0 (iPhone Mail 5G77
Apple-Mail-3--212028499
X-Mailer: iPhone Mail (5G77)
Mime-Version: 1.0 (iPhone Mail 5G77)

 

[Ledsteplin]

Welcome to iMore! Where are you seeing that? In the Mail app? I don't see anything like that anywhere.