What's *really* strange is that if I look at the raw sendmail logs on my server, the Email from email@example.com comes in, and is forwarded to gmail ... with an "OK" as the response — i.e. the gmail MTA doesn't reject the message as it ideally should. However, the Email then disappears — it's not even in my gmail spam filter ... so there is no trace of it at all. If my friend sends directly to firstname.lastname@example.org, it shows up ... since his domain sends directly and the SPF test is passed. Note that on my gmail account, I associate email@example.com with my firstname.lastname@example.org account ... so perhaps there should be a recipient test applied before SPF is tested on the sender ... although this arguably defeats the purpose of SPF.
The logical solution is to configure sendmail on my server to do Sender Rewriting — anyone have an easy FAQ to do this? But many people/domains aren't doing this ... and my Email forwarding to gmail is quite common, so I'm surprised that this issue hasn't gotten more attention. Is there another solution?"