[always_good]

    WHERE lower(email) = lower('[e-mail]')

Is simple and hits an index on lower(email).

I'm not sure ILIKE can hit an index in your example.

[olavgg]

It can if you use the pg_trgm extension, a good summary can be read here: https://niallburkley.com/blog/index-columns-for-like-in-post...