Just a Few of the Available Sites I won’t claim to be familiar with all the possible URL shortening sites you could use. Having a link shortener protects users from malicious sites that engage in spreading malware, phishing attacks, and other harmful activity. You can fill this parameter by hardcoding a value, or by using a macro from an adserver or an ad network. A circumvention could be that a website provided its own shortlinks instead of relying on a third-party shortening service – but this is not common.
If you notice a difference in how links perform against each other, you may decide to change how your emails are laid out, or you may start to pay more attention to which pictures or phrases you use. To use custom campaigns, you add UTM parameters to your URL which are then recorded in your custom analytics report. See if you are using Classic Analytics (ga.js) or Universal Analytics (analytics.js).