Base64 images in email signatures
Embedding an image directly as a data:image/...;base64 URL makes the HTML self-contained, but email clients and signature editors do not all preserve that representation consistently. SigLint flags data-URI images so they can be reviewed before installation.
Check every occurrence: SigLint reports repeated data-URI images individually and can jump back to each detected source location.
Recommended approach
For an essential logo or icon, prefer an absolute HTTPS-hosted raster image or the target client’s supported embedded-image workflow. The right choice depends on the installation environment, so this is guidance rather than an automatic rewrite.
Evidence level
This is currently a conservative cross-client heuristic. SigLint does not present it as a universal vendor guarantee. The Rules Library and methodology keep that distinction explicit.