SVG images in Outlook signatures
SVG is excellent on the web, but email signatures pass through mail clients, signature editors and copy/paste workflows that do not share one consistent SVG implementation. SigLint therefore flags SVG assets when broad compatibility matters.
SigLint’s recommendation: use a suitably sized PNG for an essential logo or social icon when dependable display matters more than vector scaling, then test the installed signature in the actual target clients.
What the checker finds
SigLint detects inline SVG markup and common .svg image references. When the same pattern appears several times, each occurrence is surfaced with a source location instead of collapsing everything into one generic warning.
Evidence level
This is currently a conservative cross-client compatibility heuristic, not a first-party Microsoft guarantee about every Outlook release. SigLint keeps that distinction visible in the Rules Library and methodology.