How to use dynamic blocks safely in templates?
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Dynamic content sounds powerful until it breaks on a subscriber who doesn't match your conditions. Here's the rule: every conditional block needs a fallback. If you're showing a product recommendation based on browse history and someone has no history, what do they see? If nothing's planned, they see broken layout or blank space. Bad. Plan a default version first, then build your conditional.
Next, text length will destroy you if you don't plan for it. A product name might be 10 characters in English and 50 in German. A short description might be one sentence or four. Your template needs layouts that stretch and shrink without breaking. Fixed heights are your enemy. Mobile is where this gets brutal. Content that looks fine on desktop overflows or collapses on phones when it's longer than expected.
The hard part: test every logical path. If you're personalizing for VIP vs. regular customers, or domestic vs. international, or new vs. returning. test each combination in your ESP's preview mode. Most ESPs let you preview as different subscriber profiles. Use that religiously. Dynamic content moves complexity from the campaign to the template. It pays to spend time testing now instead of sending broken emails later.
Related: personalization, dynamic content, spam filters.
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