During the dispatch of a regular email campaign, EXM uses only the user's client language for publishing. Sometimes, this causes unpublished content in the web database because an email campaign does not have a version in the user's client language.
To fix this issue, install the patch corresponding to your Sitecore XP or EXM version: For Sitecore XP 9.0 Update-1: https://sitecore.box.com/s/rbjjvkyw8l85bd61nghlwifs07a1e896 For Email Experience Manager 3.5: https://sitecore.box.com/s/n9dxgy6t7p77llnaqe6qqint1z3103yk For Email Experience Manager 3.4: https://sitecore.box.com/s/q71aqf98nj1xz7tamukfs6muye8udpfn