The OnMarketer Email editor is pretty good, however it does have some issues when it comes to anchor tags within the email. Here are instructions to get the anchor tags to work properly in your email.
Edit your saved email by clicking the Edit icon from the Emails tab
Click the HTML button within the email editor
You'll see a pop-up of your HTML code. Click anywhere within the pop up and press CTRL-A and then CTRL-C to copy all of the code.
Open Notepad [or equivalent text editor] and paste the code with right-click -> Paste or CTRL-V
Find ' http://app.onmarketer.com/Emails/AddEmailWizard/ ' and leave the "Replace with:" field empty
Click Replace All
Copy all of the updated code with CTRL-A, CTRL-C or right-click -> Select All and then right-click -> Copy
Go back to OnMarketer and, if the HTML code window is still displaying, remove all of the code with CTRL-A then press the Delete button on your keyboard
Paste the new code into the window with CTRL-V
Click UpdateThe best way to test your anchor links is to update the HTML code and then send a test before saving the email. Once you've received the test and ensure the links work, don't re-edit the email (unless revisions are required) otherwise you'll need to remove the link again before sending the email in campaign.
Once you've received and tested the email it's safe to click Next to save the email.