it's 100 symbols without spaces, so email shouldn't be that long, so may be: a) several cipher symbols mean 1 clear text symbol or b) you must skip some symbols

my interpretation of "if you throw a pi at the wall, does it break into chunks of two" - take pi value in binary like 11.00100100001111110110... and assume, that 1 means keep symbol, 0 means discard it, but that didn't produce meaningfull email :( Such interpratation just shows, that hint is not clear enough, too much variations.