How do you use AMPscript RedirectTo with UTM tracking parameters?

RedirectTo(url) wraps a URL with Marketing Cloud click tracking and returns the tracked URL. To append UTM parameters you build the URL string first:
%%[
SET @baseUrl = "https://example.com/product"
SET @utm = "?utm_source=email&utm_medium=email&utm_campaign=spring2025"
SET @trackedUrl = RedirectTo(Concat(@baseUrl, @utm))
]%%
<a href="%%=@trackedUrl=%%">Shop Now</a>
The outer MC tracking layer records the click against the subscriber, and the UTM parameters are passed through to GA/analytics. Ensure special characters are URL-encoded using URLEncode() if parameter values contain spaces or special characters.