Advice on migrating from one email provider to another

[MMM]

• Test new email provider
  Before migrating your email or changing MX records, test the new server thoroughly. Use an internal test environment and/or test sending emails via telnet and make sure they get delivered without issues.
  
  It may help to fully-configure a subdomain (e.g. test.you.com) to receive email to the new provider.  That way, you're able to test full send/receive functionality of the service while the current provider is still active.
  
  http://www.mxtoolbox.com is a great site that can perform many diagnostic checks for you, as well as verify that you're not putting an open SMTP relay online.
  
  
  
• Change MX records
  After fully testing the new provider and about a week or so prior to making it live, it is recommended that you add an MX record alongside your current record to point to the new provider.  This can be done whether or not the server is actually taking requests on your behalf.  This record needs to be last-in-line, so must have a high preference number.
  
  For example, if moving from Google Apps to your own server, your MX records might look like:
  

  Output of nslookup -type=mx you.com:
  
  you.com       MX preference = 10, mail exchanger = aspmx.l.google.com
  you.com       MX preference = 20, mail exchanger = alt1.aspmx.l.google.com
  you.com       MX preference = 20, mail exchanger = alt2.aspmx.l.google.com
  you.com       MX preference = 50, mail exchanger = mail.you.com
  

  
  It is also helpful to set your DNS TTL to a low value during this time so that any changes you make propagate the web faster.
  
  If you're moving from a self-managed server, on your "go live" date, you can disable external access to it on SMTP (port 25).  Anyone emailing you @you.com will attempt to contact that server first, fail, then try the new server via the MX record you added above.
  
  If you're moving from a third-party (hosted) email solution, enable email forwarding if possible to route emails from @you.com to @test.you.com (if you performed the recommendation in Step 1).  This is to catch any emails that reach it while DNS is in transition.  The night before your "go live" date, change your MX records so that you only have records for the new mail server; remove all of the older entries.  Feel free to restore your DNS TTL to the original values here if you so please.
  
  
• Move your mail!
  
  Now that the previous mail server is not receiving new emails, this is a great time to migrate your emails to the new server/provider.  If started early enough, your users' emails can be in their inboxes at the start of the day.
  
  Start your first move now!
  

[crobinson]

I have no idea what any of this means. Suggestion...laymen terms.

[frauajg]

  what are you talking about?  How about a step by step instruction that anyone can understand. I did a migration, but nothing changed.  Trying to change from comcast to gmail