Change encoded mailboxes for encrypted ones

[hubdotcom]

Otherwise they can be reversed through basic cryptanalysis

a > dd
b > de
c > df
d > d8
e > d9
f > da
g > db

A > fd
B > fe
C > ff

aa > dd50
bb > de53

etc.

Instead of using encoding, it's better to encrypt or at a minimum, hash the values using SHA-256 with a secret key known only to the server.

a + secretkey > 48ef5cd26261f69762c6a2636e3272e1fe5950e5fe4efde8b12350aca23737d7
b + secretkey > 35a3d6116e2efb06946ac9ce301696936b4a332df2eb7bbb7bbc01c161d3c743