Typically when you switch Internet Service Providers (ISPs) there is little to do aside from replacing a modem and sending your money to a different place. However, there can also be an unfortunate side effect that prevents you from sending email through Microsoft Outlook 2010. This occurs because your new ISP is blocking a specific port (port 25) used by Outlook to send mail through your account. Fortunately you can configure Outlook to use a different port instead and resume normal program operation.
Step 1: Launch Outlook.
Step 2: Click the “File” tab at the top-left corner of the window, click “Account Settings,” then click “Account Settings” again.

Step 3: Click your account, then click the “Change” button.

Step 4: Click the “More Settings” button at the bottom-right corner of the window.

Step 5: Click the “Advanced” tab at the top of the window, click inside the “Outgoing Server” field, then change the value to “587.”

Step 6: Click the “OK” button, then click “Next” and Finish to apply your changes.
If you regularly need to email the same group of people, then find out how to create a distribution list in Outlook and make the whole process much faster for the emails you send to them in the future.
Disclaimer: Most of the pages on the internet include affiliate links, including some on this site.