SPF, gmail, the cpunks list, and SFP

I hear it's possible that cypherpunks emails may be being bounced by gmail due to something called SPF. I'm not that familiar with SPF, but there's some discussion of the issue at https://serverfault.com/questions/824132/how-to-properly-configure-a-mailing... Also, if you are hand-building a communication interface for a shielded room, or don't trust your supplier, make sure you get fiberoptic cable that doesn't have the usual metallic sheathing to increase internal reflection, or you'll be putting a big antenna through a wall of your secure environment. (SFP, a mis-spelling of SPF, is an interface for fiberoptics: https://en.wikipedia.org/wiki/Small_form-factor_pluggable_transceiver )