How many email clients support word-break?

It works in 4 of 21, partial in 12, not supported in 5.

Does word-break work in Apple Mail?

word-break is partly supported in Apple Mail. Closest to Proton Mail: Apple Mail, which agrees on 203 of the 300 features both are tested on.

word-break in Proton Mail

Partial word-break is partly supported in Proton Mail.

Buggy.

Works in 4 of 21 · partial in 12 · not supported in 5

Which clients

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

Your reader in Proton Mail may not see word-break the way you wrote it, even if it looks right where you tested it.

What to do instead in Proton Mail

Outlook Windows does not wrap a URL on word-break, word-wrap, or overflow-wrap. Insert  in a cell that has a width

instead

8 lines

<table role="presentation" width="100%" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td width="100%">
      https://example.com/&#8203;very/&#8203;long/&#8203;url?token=&#8203;abc123def456
    </td>
  </tr>
</table>

Show the original

before

3 lines

<span style="word-break: break-all;">
  https://example.com/very/long/url?token=abc123def456
</span>

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What Proton Mail does with word-break

caniemail record, tested upstream 15 Feb 2022

Buggy. Supported but a word-wrap:break-word is applied, making it look like break-all.

Your next question

Every feature in Proton Mail · word-break in every client

Questions

How many email clients support word-break?: It works in 4 of 21, partial in 12, not supported in 5.
What do I use instead of word-break in Proton Mail?: Outlook Windows does not wrap a URL on word-break, word-wrap, or overflow-wrap. Insert  in a cell that has a width.
Does word-break work in Apple Mail?: word-break is partly supported in Apple Mail. Closest to Proton Mail: Apple Mail, which agrees on 203 of the 300 features both are tested on.

To see what else in your email Proton Mail does not support, paste the whole email.

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Real captures 14 Oct 2026 on 10 installs · caniemail (MIT) via @emailens/engine 0.18.22 · tested upstream 15 Feb 2022 · data last changed 10 Nov 2026 · Outlook (New) cells are the engine's mapping