[FIX] The matching operator to get patner from email in mail_thread.

The current operator is ilike but it add wildcards around right criteria so we can have false positive.

eg. I' have an email in my customer base like a_mail@provider.com

If I get a mail from mail@provider.com as ilike operator uses wildcards a_mail@provider.com can potentially be matched and retrun a faulty match.