What are fixed vs fluid layouts?

Fixed layouts have set pixel widths (typically 600px). They look consistent but don't adapt to screen size-on mobile, they shrink to fit or require zooming. Fluid layouts use percentage widths that stretch and contract with the viewport, adapting naturally to any screen size.

Trade-offs: Fixed layouts are simpler to build and more predictable across clients. Fluid layouts are more flexible but can behave unexpectedly in certain email clients. Hybrid/responsive approaches combine both-fixed structure with responsive breakpoints that reflow on small screens.

Pure fluid is rare in email; hybrid is the standard. Email clients have quirks that make pure percentage-based layouts unreliable. Most professional email design uses a fixed-width container that switches to fluid behavior below certain breakpoints (typically 480-600px). This gives you control on desktop and flexibility on mobile. Templates from reputable ESPs typically implement this approach.