HTML element · data last changed 10 Nov 2026
<base> in email clients
Works in 4 of 21. Not supported in Outlook Classic, Outlook Android and Proton Mail. Partial in Gmail, Gmail Android, Gmail iOS and 10 more. Untested in Superhuman.
Your reader in Outlook Classic sees the email without <base>, even if it looks right where you tested it.
caniemail (MIT) via @emailens/engine 0.18.22
What to do instead in Outlook Classic
There is no drop-in fix for <base> in Outlook Classic. Design so the email still reads without it.
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<base> is not among the 24 features we have screenshotted on real installs. The ones we have →
All 21 clients, problems first
| Client | Support |
|---|---|
| Outlook Classic | Not supported |
| Outlook Android | Not supported |
| Proton Mail | Not supported |
| Gmail | Partial See caveat 1 |
| Gmail Android | Partial See caveat 1 |
| Gmail iOS | Partial See caveat 1 |
| Outlook 365 | Partial See caveat 1 |
| Outlook (New) | Partial See caveat 1 |
| Outlook iOS | Partial See caveat 2 |
| Outlook for Mac | Partial See caveat 1 |
| Yahoo Mail | Partial See caveat 3 |
| Yahoo Mail Android | Partial See caveat 3 |
| Yahoo Mail iOS | Partial See caveat 3 |
| HEY Mail | Partial See caveat 1 |
| AOL Mail | Partial See caveat 3 |
| Fastmail | Partial See caveat 4 |
| Superhuman | Untested |
Works in 4: Apple Mail, Apple Mail iOS, Samsung Mail and 1 more. Show all
| Client | Support |
|---|---|
| Apple Mail | Works |
| Apple Mail iOS | Works |
| Samsung Mail | Works |
| Thunderbird | Works |
Caveats (4)
- 1. Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook (New), Outlook for Mac, HEY Mail: Buggy. The element is removed but URLs are turned into links with
hrefattribute. - 2. Outlook iOS: Buggy. The element is removed but URLs are turned into links with
hrefattribute. Buggy. URLs are computed based on the first<base>element found in the<body>. - 3. Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, AOL Mail: Buggy. The element is removed but URLs are turned into links with
hrefattribute. Buggy. URLs are computed based on the last<base>element found in the<body>. Buggy. Not supported for local anchor links. - 4. Fastmail: Buggy. The element is removed but URLs are turned into links with
hrefattribute. Buggy. Not supported for local anchor links.
Caveats as recorded by caniemail (MIT), one entry per wording.
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