Overview

To create a custom mobile subdomain on 1and1 you'll need to create a new CNAME record.  Follow the steps below.

Steps

1. Go to 1and1.com and login to your account.
2. In your account, click on the Domains tab.
   
3. Under "My Domain", click on Manage domains.
   
4. Find your domain, then click Create Subdomain.
   
5. In the "Create Subdomain" field, enter "m" (just the letter). Then click Create Subdomain.
   Note: If you get an error stating "This subdomain is not available", it means that subdomain was created already and you can skip this step.
   
6. Click on the Domains tab to go back to Domain Center, then click Manage Subdomains.
   
7. Scroll down to Subdomain Overview, then find your mobile subdomain (m.yourdomainname.com) and click on it.
   
8. Scroll down to the DNS Settings section and click on it to expand. Then click Edit.
   
9. In the next page, scroll down to A/AAAA Records (IP Addresses), then click CNAME.
   
10. In the Alias field, enter: mobile.dudasite.com
    
11. Check the box that says "I am aware and accept that all current DNS settings, e-mail addresses and redirects will be disabled", then click Save.
    
12. Hit Save one more time when the box pops up, and you're done!
    

Other Resources:

You might be looking to set-up your automatic mobile redirection with your 1and1 site builder. Please view our instructions article on it here.