Why do I see a "URL No Longer Exists" message when pressing the Preview button?

When clicking the Preview button on a Soapbox Mailer Campaign record page, you might receive an error page that has the following error message on it:  "URL No Longer Exists".  Here are the reasons why you might see this page.

1) In Salesforce, you might have clickjack protection enabled for non-setup custom Visualforce pages. You can turn this off by going to Setup > Administration Setup > Security Controls > Session Settings > Clickjack Protection:  ensure that the "Enable clickjack protection for non-setup customer Visualforce pages" checkbox is unchecked, and click the Save button.

2) Ensure that your Preview button URL is correct by going to Setup > Build > Customize > Campaigns > Buttons and Links > Custom Buttons and Links > Preview > Edit > the big text area at the bottom of the page should have:  <<Your New Site URL>>/apex/sbm__sbx_emailviewbodyhtml?id={!Campaign.Id}

NOTE: Replace “<<Your New Site URL>> with your Site URL, INCLUDING the "/track" at the end of it.

So, if your Site URL is "http://picnet.force.com/track", your URL in this big text area would be:

http://picnet.force.com/track/apex/sbm__sbx_emailviewbodyhtml?id={!...

Very often, people just forget to include the "/track" before the "/apex..." or simply have made a mistype in the URL itself.

Happy emailing!