Redirect mail traffic

We are moving Data centers. There will be a period of time where we may want to redirect mail traffic. We can used DNS but that takes time to propagate. I have used multiple irules for URL and http traffic but not for mail traffic. I don't know if F5 has the right operators for SMTP.

Basically, all traffic coming in over 995 and SMTP should be redirected to the new mail server in the new data center. I thought about replacing when http request with when "client_accepted" then maybe use string parameter but they all use to "http" too. Is there a way to direct all my mail server traffic to the new domain. Obviously, my mail servers already site behind the F5.

ltm rule mail_redirect {

  when CLIENT_ACCEPTED {

  if { [string tolower [HTTP::host]] equals "mail.olddomain.com" } {

 # redirect to mail.newdomain.com

}