Salesforce assigns your organization's account to one of its many server pods. Think of it like a physical machine, in the cloud. Sometimes, you'll need to know which Salesforce pod you're on so we can help you in troubleshooting a challenge with Soapbox Mailer. To determine your Salesforce pod ID, do the following.
1) Go to http://login.salesforce.com
2) Login with your account's credentials
3) After you've logged in successfully, note the characters in your web browser's address bar right before ".salesforce.com". It will say something like "http://na11", etc. The "naXX" is your pod ID.
4) If your domain does not have "naXX" in the web address bar, you are likely using the "My Domain" feature to customize the URL. If that's the case, select and copy what you have instead of "naXX"
5) Click to go to this tool.
6) Paste the text you copied into the field at the bottom of the form.
7) Click "Find"
You should then see the name of the server pod you are on.