How to pick up lagging e-mail after changing your mail IP

I receive e-mail mainly at a domain name that I own. I recently switched to a new web host and thereby acquired a new IP address for my e-mail. I use POP but I think that this works for IMAP too. Many (all?) mail clients (programs that run on the personal computer) cannot be told which IP address to use to fetch e-mail. Instead they use the DNS service that comes with Internet service to translate the domain name in the recipient’s e-mail address to an IP address and go there to seek incoming e-mail. Changes to DNS may take up to 48 hours. Toward the end of this period my e-mail client has already begun to fetch mail from the new IP address. For those who send me mail and whose DNS is tardy their e-mail for me will go to the old server and my client will never see it.

There is a simple solution on the Mac but you must know the IP address of the name server of the old hosting service. When you own a domain name it is via a registrar and when you switch your domain name to be served by another physical host you inform your registrar of the new name server under control of the hew hosting service. As you notify your registrar you can (probably) discover the identity of the old name server which you will need for this trick. With Network Solutions (my registrar) you deal not with IP addresses but with the domain name of a name server. (Yes name servers have their own domain name.) To discover the IP address of any domain name, such as the domain name of the name server, you can type the following command into the Terminal Utility:

In the voluminous response you will find text like this:
In the above case the IP address for that domain is “”. After you have waited long enough (48 hours?) and when you have the IP address of the old name server do: Your mail client should now have all of the trailing e-mail.

I had two accounts with the same e-mail address one with the old and the other with the new password. That way I did not have to switch passwords as one would always fail and the other succeed.