Desktop Outlook blocks hosted images by default (mobile shows them fine). Two fixes:
Quick (fixes your own view): Outlook → Options → Trust Center → Trust Center Settings → Automatic Download → untick “Don’t download pictures automatically”.
Bulletproof (all recipients, recommended): embed the logo inside the signature —
1. Paste the signature as normal (the logo may show as a broken box).
2. Download the logos:
GS Group ·
Optronix
3. In the signature editor, delete each broken image box and insert the matching downloaded file in its place (Insert → Pictures, or drag it in). Note: embedded images lose their hyperlinks in most clients.
4. Save. The logo now travels inside every email — nothing to block, works everywhere.
Use the PNG, not WebP — classic Outlook on Windows cannot display WebP at all.