Write a web page today and you reach for flexbox or grid, put your styles in a stylesheet, and expect it to work. Write an email and none of that is available.
The reason is specific rather than general neglect: Outlook on Windows does not render email with a browser engine. It uses the one from Microsoft Word, which was never a layout engine for the web and does not pretend to be.
What actually does not work
| Technique | In email |
|---|---|
| Flexbox and grid | ignored entirely |
| External stylesheets | stripped by every major client |
<style> in the head |
stripped by some, including Gmail on forwards |
| Float | unreliable |
| Padding on non-table elements | inconsistent |
| Background images | blocked or ignored in several clients |
| Web fonts | mostly ignored, falls back |
What is left is tables for layout and a style attribute on every element. That is how web pages were built in 1999, and it is not nostalgia — it is the only thing that renders the same in Outlook, Gmail, Apple Mail and the rest.
Why are images such a problem?
Because most clients block them until the reader asks for them. Outlook, Gmail and Apple Mail all default to not loading remote images, on the reasonable grounds that a remote image is a tracking pixel with a picture attached.
So a signature built around a logo arrives, on first contact with a new correspondent, as a broken-image placeholder. That is the worst possible moment for it.
Embedding the image as a Base64 data URI seems like the fix and is not: Gmail and Outlook both strip or refuse data-URI images in mail. The reliable options are an attached image referenced by content ID, which has its own problems, or no image at all.
A text signature always renders. That is worth more than a logo that sometimes does.
What about the confidentiality disclaimer?
Those long footers have close to no legal effect in most jurisdictions, for a straightforward reason: you cannot impose obligations on somebody by sending them an email they did not ask for. A contract needs agreement, and receiving a message is not agreement.
They persist because someone once advised a legal department that they might help, and removing them requires a decision nobody wants to be responsible for.
If your employer requires one, include it. If the choice is yours, the space is better used on nothing at all.
How long should a signature be?
Four lines or so. Name, role, one contact route, one link.
The reason to keep it short is that it appears on every message you send, including the one-word replies and the "thanks" at the end of a thread. A ten-line signature turns a two-word answer into a page, and in a long thread it repeats down the whole quoted history.
Anything that is a marketing message rather than contact information belongs in the message.
Questions people ask
Why does my signature look different in Outlook? Because Outlook is not rendering the same way as everything else. Test there specifically; if it works in Outlook it works everywhere.
Can I use a web font? It will be ignored in most clients and fall back. Pick a fallback stack you are happy with, because that is what most people will see.
Should I include social icons? They are images, so they are blocked by default. Text links work.
Does dark mode break signatures? Frequently. Some clients invert colours, which can turn a dark logo invisible. Another argument for text.
The email signature generator produces table-based HTML with inline styles and no images, and the signature generator makes the handwritten kind for documents rather than mail.