MX Records for email question?

I'm not sure if I need to do anything else regarding email setup from my old host. Once I make the following change on my domain registration account (not dreamhost)

In reply to:

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... You'll need to login to the control panel with your current host (or contact their support team) to modify the nameservers to the following:

ns1.dreamhost.com 66.33.206.206
ns2.dreamhost.com 208.96.10.221
ns3.dreamhost.com 66.33.216.216

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Does this change automatically allow dreamhost to start receiving my mail at @myhostname.com? or do I have to modify some MX email setting on my old host?

and if so, since it take a while for this name server change to happen, won't some of my email go to my original host during this change?

This will make dreamhost the recipient of your mails, since the MX-record is looked up in the DH nameservers.

It requires two things:
1) That you add the email-addresses you need in the DH panel
2) You wait for DNS to be updated on the nameservers around the world

emails accounts at dreamhost have been configured, so all I need to do is change the DNS settings on my domain registration site.
Thank you.

...and wait. Yes, some mails will arrive at your old host, and some at DH. DNS-servers do not update at the same time around the world.