How to change hosts without losing emails
When you change hosts you must make a change to your domain name to point to your new host's name servers. While it's any easy step generally, it does create a frustrating period of time called "propagation". Propagation is the time it takes from when you make a change to your domain name until the time it takes for the whole world to see the change. This time usually spans anywhere from 24 to 72 hours. Why? Well, really simply put - when you made that change, the place you made the change at must tell thousands of other servers around the world that the change has been made. Some servers request change information every 12 hours, some not but every few days. So - DNS servers use sort of a "virtual word-of-mouth" to update one another, and it simply takes a day or so for the news to spread.
During propagation there is a chance your emails will go to your old host, or they may go to their new host, depending on whether or not the sender's ISP's DNS is updated or not. You can't afford to lose emails or even risk delayed replies, so what do you do? Actually, it's quite easy.
Step 1. Setup Email Accounts With ModHost
Go ahead and activate your new web hosting plan, if you have not already. For this example, let's assume you use the address sales@yourdomain.com as your email address. Create a new email account on your new hosting account called sales@, just like your old host.
Step 2: In Outlook Change Your Current Sales@ POP
In Outlook (or whatever your email application is) click to edit the properties of your sales@ account. Most likely your POP and SMTP settings are mail.yourdomain.com. Change your POP settings to the IP address of your old hosting account. Don't know that IP address? Just ping it. ( http://network-tools.com/ )
Step 3: Create a New Duplicate Account In Outlook
In Outlook (or whatever program) create a new email account - this will basically be a duplicate of your current sales@ account. Feel free to go ahead and set your SMTP server still as mail.yourdomain.com but set your POP to the IP address of your new hosting account. If you are using ModHost you can find this IP address in your welcome email.
Step 4: Just Check Both Accounts for a Few Days
That's it - you now have 2 sales@ accounts, one that checks your old hosting account and one that checks your new account. When you click "Send / Receive" both account will automatically be checked. You should only have to do this for a few days after you initiate your domain name change and then can delete the sales@ account that checks the old host.
Step 5. Cancel Your Old Host
You may now cancel that old hosting account.