Which email clients support HTML signatures? A compatibility table from vendor pages

Among the email clients that support HTML signatures, only a few say so on their own help pages. Zoho Mail and Spark describe an HTML option. Most others describe a rich-text box where you format text and add pictures. At least one, iCloud Mail on the web, says plain text only. This table is built from ten vendor pages we opened on 5 October 2026, and where a page is silent, the table says so instead of guessing.

Email clients that support HTML signatures: ten apps, ten pages

Each row reports what the vendor’s own page says. “Not described” means the page is silent, not that the feature is missing.

App	Does the page describe pasting HTML?	What the page says about formatting, images, links	Phone apps on that page
Gmail (computer)	Not described	Format text and add images; up to 10,000 characters	Android and iPhone tabs exist; the text we read covered computer steps
New Outlook, Outlook on the web	Not described	Text, links, pictures, fonts, colors, styles, alignment; for complex layouts, build in Word and paste	Not covered on that page
Classic Outlook (same Microsoft page)	Not described	Same list; warns that VML tags can make elements show as attachments instead of inline images	Not covered on that page
Outlook for iOS and Android	Not described	Not stated; the page gives the Settings, Signature path and a per-account toggle	This is the phone page
Apple Mail on Mac	Not described	Formatting and link tools in the Edit and Format menus, image insertion	Not covered on that page
iCloud Mail on iCloud.com	Not described	Plain text signature only	Not covered on that page
Zoho Mail	Yes: an Insert HTML option in the editor	Images in GIF, JPG, JPEG, BMP, PNG; formatting is not shown when composing in plain text	Not mentioned
Proton Mail	Not described; the page says to paste a signature from an external builder	Text style, size, color; images, lists, quotes; recipients need remote content on to see images	Not mentioned
Spark	Yes on Mac, Windows (an HTML button) and iOS (paste HTML code)	Images through a toolbar icon on Android, and a long tap on iOS	Android and iOS covered
Yahoo Mail (desktop web)	Not described	Not stated; the page covers a toggle and a text box	Not covered on that page

That is the whole table. Anything that isn’t in a cell is a question for you to test, not a fact we know.

How to read the table of email clients that support HTML signatures

Three patterns show up.

Code in, code out. Zoho’s page and Spark’s page both mention an HTML route. If your signature already exists as HTML, these are the shortest paths. Even there, Zoho’s page does not say how much code the box takes, so keep the markup lean.

A box that formats, not one that takes code. Gmail, Outlook, Apple Mail and Proton describe an editor with toolbar tools. None of those pages tells you to paste source code. The usual workaround is to open the HTML in a browser, select what you see, copy and paste. Microsoft recommends a close cousin of this for complex formatting: build the signature in Word, then paste it into the signature box. Proton’s page also says you can copy a signature from an external builder and paste it in.

Plain text. Apple’s iCloud page states the signature is plain text only, so there is nothing to design there except line breaks and wording. Our plain text email signature article covers that case.

What “support” can mean for HTML signatures

When people search for email clients that support HTML signatures, they may mean three different things, and the vendor pages answer only the first two:

1. You can type or paste a layout into the signature box. Most rows above.
2. The app will keep the layout when it sends. The pages say little about this, which is why testing matters.
3. The recipient’s app will draw it correctly. That depends on the other side, not on your signature box.

A signature can pass the first and still fail the third. For Gmail’s side of the third, Google’s CSS page, last updated 15 September 2026, says Gmail might ignore unsupported CSS properties and selectors. Our guide to the HTML email signature covers which markup survives.

An app that is missing from the table

We planned to include one more popular desktop client. Its vendor page did not load in the tool we used to read it, so we left it out. We did not fill the gap from memory. If one of your team’s email clients that support HTML signatures is not in the table, open its help page and look for the words “HTML”, “paste”, “images” and “plain text”.

A 15-minute test for email clients that support HTML signatures

You do not need a lab. You need two or three mailboxes, and the same steps work for any row in the table.

1. Build the signature in one place, and open it in a browser to confirm it looks right.
2. Put it into the app you are testing, by the route that app’s page describes.
3. Send a new message to a Gmail address, an Outlook address, and one on another provider.
4. Open each on a computer and on a phone.
5. Turn images off in one recipient app and check that the name, title and number are still readable as text.
6. Reply to one of the messages and see what the signature does in the thread.
7. Switch a message to plain text and see what remains.

Write down what you see in a small grid, sender app down the side, receiving app across the top, and mark each cell fine, shifted or broken. That grid is more useful than any general list, including ours.

A layout to run through the test

Use something with a logo, a few text lines and some links. Here is one from emailfooter:

Profile layout. The company and person are made up.

It is built from tables and inline styles, the approach our HTML guide explains. emailfooter lets each person copy the finished signature and follow steps for 16 mail apps, so you can run the grid above with a real file.

Fixes when email clients that support HTML signatures break the layout

• Plain text mode. Zoho’s page says formatting is not shown when composing in plain text. Check the composing mode before you check the signature.
• Pictures show as attachments. Microsoft’s page names VML tags as a cause in Outlook.
• No images at all. Proton says the recipient must allow remote content. Keep key details as text.
• Layout shifts after paste. Paste into an empty box, and clear any old signature first.
• Gmail is cutting your signature. Google’s page gives 10,000 characters and does not say how code is counted, so keep the markup short.
• Phone looks different from desktop. Phone apps have their own signature settings, as Microsoft’s Outlook mobile page shows. See mobile email signatures.

For the full setup walk-through, read how to set up an email signature.

Choosing between email clients that support HTML signatures

If you are picking a mail app for a team and an HTML signature matters, make the table above your starting list and your own grid the deciding vote. If you already have an app, find its row and follow the route it names. For a company where staff use different apps, one shared design with per-app install steps is the practical answer. emailfooter does that, and it does not install signatures into mailboxes for anyone.

Frequently asked questions

Which email clients support HTML signatures?

On their own help pages, Zoho Mail and Spark describe an HTML route. Gmail, Outlook, Apple Mail on Mac and Proton Mail describe rich-text editors, and iCloud Mail on the web says plain text only.

Can I paste HTML code into a Gmail signature?

Google’s page describes formatting text and adding images, not pasting code. The common method is to copy the rendered signature from a browser and paste it into the box.

Do email clients that support HTML signatures show them to every recipient?

Not necessarily. How the message looks depends on the recipient’s app, so send test messages to several.

How do I test email clients that support HTML signatures?

Send one message from your app to several others, on computer and phone, with images on and off, and compare what arrives.