What are “linked” vs “embedded” images?

Linked images reference external URLs; the email client fetches them when the email is opened (or when the recipient enables images). Embedded images are attached to the email itself and referenced via Content-ID (CID), traveling with the message.

Linked advantages: Smaller email size (just URLs, not image data). Cacheable and updatable (change the hosted image, all views update). Standard practice for marketing email. Linked disadvantages: Requires image loading (blocked by default in some clients). Dependent on hosting (if CDN fails, images break).

Embedded advantages: Display immediately without loading delay. Survive forwarding intact. Embedded disadvantages: Increase email size significantly. Can trigger spam filters. Inconsistent client support. Use linked images for marketing email. CID-embedded images have specific use cases (some transactional emails, Outlook-heavy B2B) but aren't the default choice.