I am stuck there too. I'm almost certain it requires sending an email to a gmail address, but I'm not sure what that address is. I've already tried:
No response:
3.243f6a8885a@gmail.com (hexadecimal representation of pi to 11 digits)
3.243f6a8885a3@gmail.com (hexadecimal representation of pi to 12 digits)
182d4454fb210940@gmail.com (IEEE double precision representation of pi, little endian)
Address not found:
3.14159265359@gmail.com
pi@gmail.com
ea2e4454fb210940@gmail.com (IEEE double precision representation of 3.14159265359, little endian)
3.243f6a88876@gmail.com (hexadecimal representation of 3.14159265359, no rounding)
3.243f6a88877@gmail.com (hexadecimal representation of 3.14159265359, rounding)
332E3134313539323635333539@gmail.com (ASCII string 3.14159265359 in hexadecimal form)
7069@gmail.com ('p' and 'i' ascii codes to hex)
But I'm starting to think maybe my idea of using the hexadecimal representation of pi is a red herring. I also hope I'm not hitting gmail's spam filters.
lbh ner ba gur evtug genpx gung vg vaibyirf fraqvat na rznvy, Cv (fcrpvsvpnyyl gur cerpvfvba bs Cv cebivqrq), naq urknqrpvzny ahzoref. lbh ner hasbeghangryl qbvat gur rapbqvat vapbeerpgyl, V jbhyq gel qbvat vg gur jnl n crefba jub qbrfa'g xabj nalguvat nobhg ahzoref, onfrf, sybngvat cbvag, rgp jbhyq qb vg. vg'f abg n "pyrire" fbyhgvba.