Support has said that this is the result of something (automated or otherwise) messing around with the Marketo tracking links
I don't fully buy this explanation (which is echoed in a Marketo support post).
It's absolutely true that mail security software rewrites links (which have already been rewritten by Marketo). So you might have http://www.example.com/landingpage rewritten to http://click.example.com/12qf832akadsf for click-tracking purposes when it's sent out, then rewritten again by the recipient's mailserver to http://mailprotect.mycompany.com/protected/453jnge872356t?thengoto=http://click.example.com/12qf832akadsf.
The lead will see the http://mailprotect.company.com/... URL in their inbox. And it's certainly possible that if the http://click.example.com/... URL is long, the MailProtect URL may end up truncating the original http://click.example.com/... URL that's encapsulated inside the MailProtect URL.
But that doesn't explain how the lead could register a Clicked Email in the correct campaign yet have the URL reported as malformed. Try truncating a Marketo click tracking URL by trimming off the last alphanumeric character. Chances are 99.9999% you'll get a 404 error with "The redirect URL is empty." And I have no reason to believe that this type of "malformed URL" gets logged to the correct campaign -- rather, it doesn't get logged anywhere at all.
So I'd instead be looking into links that were malformed from the start -- I know you use Velocity, so have you exhaustively tested for exceptions (null values, missing array indices, etc.)?
Great thoughts Sanford.
There is always a possibility of the Velocity scripts doing something funky. But...my gut feel is that this shouldn't be a problem in the send where the malformed links are being registered.
Our newsletter has some scripts in it, but they only affected the footer, and a minor story in the middle. There's no way these pieces could account for anything like the volume of link clicks that appear to be malformed. It seems more like the number of clicks we would get to a featured story somewhere up the top - which are all static pieces of HTML.
Having said that, your explanation makes a lot more sense than anything else. So I'll do some digging when I get a chance. Thanks again!
Thinking about it....could I run a smart list based on "clicked link is malformed link"? Or something similar? To try and find the specific leads that clicked the link?
If that's possible, then I could theoretically click every link sequentially from my profile and see which one turns up as a "malformed link" in my activity record.