Why consistency matters more than the tags
Analytics treats Newsletter, newsletter and news letter as three different sources. Six months of that and no report adds up. The builder lowercases everything, turns spaces into underscores and remembers the sources you have used, so the next link matches the last one.
Which tags to use
- utm_source — where the click came from:
newsletter,linkedin,partner_site. - utm_medium — the kind of channel. GA4 groups channels by this value, so stick to its conventions:
email,cpc,social,referral. - utm_campaign — the campaign or promotion.
- utm_content and utm_term — to tell apart links in one message, or paid keywords.
Never tag internal links between your own pages: each click would start a new session and erase the real source.