How have you set up your smart campaign filters to handle click activities from spam filters?
Right now I'm getting a ton of clicks on single emails because of spam crawlers, which is then leading to bad MQLs. I was able to stop the MQLs by adding an "opened email" trigger to the clicked smart list, but I may be missing leads who are clicking emails from right within their client without opening the email.
There's no accurate way to detect these automated activities, for reasons explored in numerous other threads.
I have resorted to including an invisible URL link in my email template footer. Robots will click on the invisible URL, but humans will not. In my campaigns for checking whether a valid email link has been clicked, or whether to promote someone to MQL, I check to see if the invisible link has been clicked. I include either a Trigger or Filter along the lines of Clicks Link in Email: [name of email] Link: is not [URL of invisible link].
Regarding the invisible link, I find an inconspicuous space in my template footer and create a tiny-text link the same color as the background.
I hope this helps.
Except if you screen out any lead who's had a bot click the invisible link on their behalf, you're ignoring the moment when the actual human clicks visible links in the email.
There have to be more constraints on such a process (and Marketo does not currently offer the granularity to deal with this problem using Smart Lists alone).