I'm using a 3rd party software called voluum to track visitors from an email. A campaign in market has 5000 clicks, but the volume link has less than 200.
I think it's possible the 3rd party software to track links is malfunctioning or it could be my user error, but does marketo block certain tracking?
Does anyone else feel like the link clicks in marketo are not accurately reported?
Link clicks are susceptible to activities from email scanners and hence, are not a very reliable source of real-person engagement. It could have been the case that Marketo may not have filtered out the susceptible bot activities from the act log, unlike the third-party platform, and that's where potentially the difference in the click link counts could be coming from. I don't know the exact nitty-gritty of it, but probably there also could be a difference in the way both platforms track the click-link engagements, and that could also be the reason you're seeing a difference in the counts.
Marketo registers only a single activity for the email opens for the person-email asset combo, but that's not the case with email clicks, multiple clicks by the same person on the same email asset's link are logged each time the person (or email scanner) clicks it in the activity log. Also, just to verify, I hope you're checking the same type of metric in both places, i.e., either unique clicks or total clicks in both places, and not checking different (unique/total clicks) metrics.
Totally agree with everything @Darshil_Shah1 said.
You'll first want to know is how Marketo is treating bot activity in your instance. If it's only logging, but not filtering out, you can create a smart list of records that have a link click attributed to them, but then add the constraint of "Bot activity is TRUE". If there are a lot of those records, or perhaps some of those records are showing multiple clicks to the same link within their activity log, that could definitely explain the discrepancy.