While waiting for the response from the support team, I'd like to hear from my peers here.
I had an email asset with a link that has mtk_tok enabled; the link worked properly during the test, meaning the link opened. Believing the test result, we sent out the email, and many responded to us "the link isn't working". I realized that the length of the mkt_tok is significantly different (60 more chars, to be precise) so that the page has returned 414 error (URL too long).
Though there seems to be some resolutions on the website server end, I wonder if somebody else noticed this before.
This is a misconfiguration of your webserver. Not sure what else to say, except it's not a sign of a mature web team that they would set a URL length limit below real-world needs. What are they trying to solve exactly? Is the webserver code actually vulnerable to an overflow attack?
I know what needs to be fixed on the web server end My question was if anybody has noticed the length of mkt-tok changes between test and actual emails. Maybe not a big deal for many people though.
On a side note, I highly recommend testing your emails as a recipient to ensure you're testing real-world scenarios and not defaults prior to launching a campaign. You can do this by previewing the email as a recipient and/or sending yourself a test as that person(s).