Adjusting the mail flow is an important step in the onboarding process. This is where you are presented with the new MX records. On this stage, you can change current MX records for the domain name.
Read the Knowledge Base article on What Is An MX Record? What Is The Correct Syntax For MX Records? What Is Priority? and on What Is DNS Propagation? for more information. Before changing MX, you need to select one of the two options available:

  • Mail Filter Redirection Disabled: You may not need Mail Filter Redirection (MFR) in the Onboarding process if the MX records for the domain name point to a 3rd party filtering or archiving solution or a POP server, i.e. the MX records do not point directly to the Exchange mail server and you plan on using 3rd party services in the future. With such kind of mail flow setup, there is usually redirection or forwarding from the 3rd party server to an Exchange server. In this case, this forwarding or redirection settings are changed later at the time of cutover on the 3rd party server.

  • Mail Filter Redirection Enabled: You may need MFR if the MX records for the domain name point directly to the mailing server and thus need to be changed as the mailing server changes. With the MFR enabled, we redirect all incoming mail for this account to the current server at the mailfilters. The purpose of such setup is to have all mail received at one server (the old one) while the new MX propagates. This way the users will not get confused at mail going to different servers (for the old MX (cached) and the new MX (propagating)) as all mail will be delivered to the old server only.
    You may also need redirection enabled if you use 3rd party filtering or archiving solution or a POP server, but do not plan on using it any more after cutover.
    If you enable MFR you need to enter the following settings:
    • SMTP server: Your current MX server name.
    • Port: 25.

      Important note: The server that is used for redirection must respond via the port specified. To check if the server responds via this port, go to Start > Cmd, type in "telnet servername port#" without the quotes where "servername" is one of their current MX records and "port#" is the port number and press Enter. You should not encounter any errors.
  • Change MX records if necessary. The server names for MX destination are presented on this step. You may need to contact the DNS provider to change the records or change them yourself if you have admin access to the name servers. After making necessary changes to the DNS records click Start Migration.