I missed a couple of important e-mails while I was in Norway this past week. Although I was checking my metalab.unc.edu e-mail at least once a day, several important responses somehow went to my GMail address instead, which I was not checking. I found them when I got home and opened my Gmail account yesterday.
At first I was perplexed, because I do not usually set my return address to GMail. Then I remembered that on the road I was using the GMail SMTP server to send, because the Speakeasy server I normally use only works from my local area network behind my router. Could GMail be rewriting my headers? So I did some experiments.