When you click a hyperlink in Outlook 2007 or 2010 with Internet Explorer set as the default, the Open With window ("How do you want to open this?" dialog) appears with the list of browser choices. This is an issue in Windows 10 with Outlook 2007 or 2010 installed, and Internet Explorer set as the default browser.
Although you click the Always use this app checkbox and click OK, Outlook shows the same prompt the next time you click on a web address or hyperlink in email. The Microsoft article You are prompted to specify Internet Explorer when you click a link in Outlook 2010 or Outlook 2007 works for a vast majority of users, and this post simply condenses that information, providing a registry fix and a command-line option to automate the setting.
Download outlook-ie-opennew.zip, unzip and run the outlook-ie-opennew.reg. This creates the following registry key:
And sets its (default) value data to:
"%ProgramFiles%\Internet Explorer\IExplore.exe" %1
Using Reg.exe Command
Alternately, you can simply open an administrator Command Prompt, and run the following reg.exe command.
Right-click Start, click Command Prompt (Admin). Type in the following command and press ENTER:
reg add "hkcr\htmlfile\shell\opennew\command" /ve /d "\"%ProgramFiles%\Internet Explorer\IExplore.exe\" "%1"" /f
You should get the message "The operation completed successfully". That fixes the Outlook hyperlink problem.