box-sizing in Outlook 365
Works box-sizing works in Outlook 365.
Works in 16 of 21 · not supported in 5
Which clients
- Works
- Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook (New), Outlook iOS, Outlook Android, Outlook for Mac, Apple Mail, Apple Mail iOS, Samsung Mail, Thunderbird, HEY Mail, Proton Mail, Fastmail, Superhuman
- Not supported
- Outlook Classic, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, AOL Mail
The fix for the clients that need it
Needed in 5 of 21: Outlook Classic, Yahoo Mail, Yahoo Mail Android and 2 more.
Account for padding in width manually (no box-sizing)
<div style="width: 300px;">
<div style="padding: 20px;">
Content; padding on inner element
</div>
</div>Show the original
<div style="width: 300px; padding: 20px;
box-sizing: border-box;">
Content; total width stays 300px
</div>A free account opens all 21 clients and keeps your checks for 7 days. Create a free account →
What Outlook 365 does with box-sizing
The Emailens probe for box-sizing on a real install counted as Outlook 365, captured 14 Oct 2026. It shows the probe, not the fix. Where box-sizing is supported it shows: both bars the same width.
caniemail: box-sizing works in Outlook 365.
This Outlook.com install drops the <style> in the head, so only inline styles apply.
Your next question
- Does animation work in Outlook 365?
Works in 5 of 21 · partial in 1 · not supported in 15
fix - Does transform work in Outlook 365?
Works in 7 of 21 · partial in 1 · not supported in 13
fix - Does overflow-wrap work in Outlook 365?
Works in 2 of 21 · partial in 3 · not supported in 13 · 3 untested
fix - Does bimi work in Outlook 365?
Works in 9 of 21 · not supported in 11 · 1 untested
- Does clip-path work in Outlook 365?
Works in 8 of 21 · not supported in 13
- Does block-size work in Outlook 365?
Works in 7 of 21 · not supported in 13 · 1 untested
Questions
- How many email clients support box-sizing?
- It works in 16 of 21, not supported in 5.
- Does box-sizing work in Outlook (New)?
- box-sizing works in Outlook (New). Outlook 365 and Outlook (New) differ on 1 feature: text-shadow.
To see what in your email Outlook 365 does not support, paste the whole email.
No signup · Five clients free, Outlook Classic included · All 21 with an account
The checker needs a computer screen.
Real captures 14 Oct 2026 on 11 installs · caniemail (MIT) via @emailens/engine 0.18.22 · tested upstream 28 Feb 2019 · data last changed 10 Nov 2026 · Outlook (New) cells are the engine's mapping