class EventMailer < ApplicationMailer
  def event_info(to, email)
    @email = email
    mail(to: to,
         subject: @email[:subject])
  end
end

class EventMailer < ApplicationMailer
  def event_info(to, email)
    @email = email
    mail(from: @email.user.email,
         to: to,
         subject: @email[:subject])
  end
end

Set the From in the event mailer to the user sending the mail
Set the From in the event mailer to the user sending the mail
