This is extracted from my other private RoR project, where I used to use Google mail to send emails and need to be careful not to send too many emails in a short time and not too many emails for every day. Now I switched to a comercial email sending services so this piece of code is no longer needed. Hopefully, it can be useful for anybody who want to send email with throttle control.
You need sidekiq to make this piece of code work.
And in an initializer, put:
ActionMailer::Base.register_interceptor(EmailThrottle::MailInterceptor)