Determine mail protocol from header?

I’m testing some address verification emails, and I want to ensure that I use the mail protocol, rather than smtp, to get the higher hourly throttling limit.

I’m seeing substantially the same headers when I send using both protocols. Is there any way for me to ascertain that the protocol I think I am using is the one that I am actually using?

If it makes any difference, it’s a PHP app (the CodeIgniter 2.0.1 email class, with prefs stored in a config file)


2056 views and nobody has anything?

FTR, I forced an error and was able to surmise from the debug info that I was indeed using different protocols.