Most email systems ask for an update each hour if a short interval such as 3,600 seconds (one hour) is set. Setting the interval ...

Most email systems ask for an update each hour if a short interval such as 3,600 seconds (one hour) is set. Setting the interval as low as 300 seconds (5 minutes) is OK. We recommend that you set the interval at least this low before you start the email migration. This setting allows all the systems that send you email enough time to process the change. Then, when you make the final switch over to %BRAND_OFFICE_365_SHORT%, you can change the TTL back to a longer interval.