Should I use tags in HTML email?

HTML element · data last changed 10 Nov 2026

in email clients

Works in 20 of 21. Untested in Superhuman.

caniemail (MIT) via @emailens/engine 0.18.22

Check your email, free

No signup · Five clients free, Outlook Classic included · All 21 with an account

The checker needs a computer screen.

A free account opens all 21 clients and keeps your checks for 7 days. Create a free account →

is not among the 24 features we have screenshotted on real installs. The ones we have →

All 21 clients, problems first

Client	Support
Superhuman	Untested

Works in 20: Gmail, Gmail Android, Gmail iOS and 17 more. Show all

Client	Support
Gmail	Works
Gmail Android	Works
Gmail iOS	Works
Outlook 365	Works
Outlook (New)	Works
Outlook Classic	Works
Outlook iOS	Works
Outlook Android	Works
Outlook for Mac	Works
Apple Mail	Works
Apple Mail iOS	Works
Yahoo Mail	Works
Yahoo Mail Android	Works
Yahoo Mail iOS	Works
Samsung Mail	Works
Thunderbird	Works
HEY Mail	Works
Proton Mail	Works
AOL Mail	Works
Fastmail	Works

How behaves

works in every email client tracked here, so the questions are size, spacing and line height, not support. Unstyled text comes out at different sizes in different clients, and Outlook Classic has its own rules for line-height, padding and borders on paragraphs.

Unstyled text size differs by client: in October 2026 we measured 12px in Apple Mail and 11pt in Outlook for Mac. Set font-size and line-height on every paragraph rather than relying on the default.
Outlook Classic ignores a unitless decimal line-height such as 1.5, and treats a px line-height as a minimum. A whole number such as 2 counts single-spaced lines. Use px, with mso-line-height-rule: exactly when the value must hold.
In Outlook Classic, consecutive paragraphs with the same border draw as one block: no border and no padding between them, only after the last. Divs with the same border do not merge. We measured this in Outlook Classic for Microsoft 365 in November 2026.
Outlook Classic applies padding on a paragraph only against a border. With border-bottom alone, padding-top adds nothing.

Set margin: 0, font-size and a px line-height inline on every , then space paragraphs with margin-bottom or with padding on the surrounding table cell. Give a divider line its own table row instead of a border on the paragraph, so Outlook Classic cannot merge it into the paragraphs around it.

Questions