How many email clients support ?

It works in 10 of 21, partial in 4, not supported in 7.

Does work in AOL Mail?

works in AOL Mail. Closest to Outlook Classic: AOL Mail, which agrees on 206 of the 298 features both are tested on.

<form> in Outlook Classic

Not supported <form> is not supported in Outlook Classic.

Works in 10 of 21 · partial in 4 · not supported in 7

Which clients

Works: Gmail, Gmail Android, Outlook iOS, Outlook Android, Apple Mail, Apple Mail iOS, Yahoo Mail Android, Samsung Mail, Thunderbird, AOL Mail
Partial: Gmail iOS, Outlook 365, Outlook (New), Outlook for Mac
Not supported: Outlook Classic, Yahoo Mail, Yahoo Mail iOS, HEY Mail, Proton Mail, Fastmail, Superhuman

Your reader in Outlook Classic sees the email without <form>, even if it looks right where you tested it.

The fix for Outlook Classic

Replace embedded form with a link to a hosted form

after

13 lines

<table role="presentation" cellpadding="0" cellspacing="0">
  <tr>
    <td style="background-color: #6d28d9; border-radius: 6px;
               padding: 12px 32px;">
      <a href="https://example.com/subscribe"
        style="color: #fff; text-decoration: none;
               font-family: Arial, sans-serif;
               font-weight: bold;">
        Subscribe Now
      </a>
    </td>
  </tr>
</table>

Show the original

before

4 lines

<form action="/subscribe" method="POST">
  <input type="email" placeholder="Email" />
  <button type="submit">Subscribe</button>
</form>

Test this fix in Outlook Classic, free

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What Outlook Classic does with <form>

@emailens/engine 0.18.22 on the original code

Outlook Classic strips form elements.

Your next question

Every feature in Outlook Classic · <form> in every client

Questions

How many email clients support <form>?: It works in 10 of 21, partial in 4, not supported in 7.
What do I use instead of <form> in Outlook Classic?: Replace embedded form with a link to a hosted form.
Does <form> work in AOL Mail?: <form> works in AOL Mail. Closest to Outlook Classic: AOL Mail, which agrees on 206 of the 298 features both are tested on.

To see what else in your email Outlook Classic does not support, paste the whole email.

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caniemail (MIT) via @emailens/engine 0.18.22 · tested upstream 10 Sep 2019 · data last changed 10 Nov 2026 · Outlook (New) cells are the engine's mapping