Does hashing PII in logs provide any real security? I have PII in my logs that I would like to replace with hashes (e.g. sha3-256(salt + email)). The idea is that I can always go back to my logs and find all the log lines with that email address, by searching on the hash result of sha3-256(salt + email).
How hard would it be for folks to retrieve the original email address? I'm assuming the salt is fixed, and kept secret and the salt is &gt;= 32 bytes.
Will this setup provide any real security if the logs are leaked?
/W
Will this setup provide any real security if the logs are leaked?

One issue is the fixed salt.  With that, the translation of email to hash is fixed; that is, if the attacker sees two identical hashes, he knows that they were the same email address; he might not know what the email address is, but he knows that the two emails were to/from the same person.  And conversely, if the hashes were different, then they referred to two different email addresses.
One possibility would be to include a 'per-hash' salt (salt1), which is randomly selected each time you generate a hash [1], and so the email address would be replaced by salt1 + sha3-256( salt + salt1 + email ) (where + is string concatenation).

[1]: You could generate the per-hash salt sequentially if the order you generated the hashes didn't need to be secret; this would allow the per-hash salt to be shorter without worrying about duplications.