CSS property · data last changed 10 Nov 2026
flex-basis in email clients
Works in 13 of 21. Not supported in Gmail, Gmail Android, Gmail iOS and 5 more.
Your reader in Outlook Classic sees the email without flex-basis, 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 flex-basis in Outlook Classic. Design so the email still reads without it.
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flex-basis is not among the 24 features we have screenshotted on real installs. The ones we have →
All 21 clients, problems first
| Client | Support |
|---|---|
| Gmail | Not supported See caveat 1 |
| Gmail Android | Not supported |
| Gmail iOS | Not supported |
| Outlook Classic | Not supported |
| Yahoo Mail | Not supported See caveat 2 |
| Yahoo Mail Android | Not supported |
| Yahoo Mail iOS | Not supported |
| AOL Mail | Not supported |
Works in 13: Outlook 365, Outlook (New), Outlook iOS and 10 more. Show all
| Client | Support |
|---|---|
| Outlook 365 | Works |
| Outlook (New) | Works |
| Outlook iOS | Works |
| Outlook Android | Works |
| Outlook for Mac | Works |
| Apple Mail | Works |
| Apple Mail iOS | Works |
| Samsung Mail | Works |
| Thunderbird | Works |
| HEY Mail | Works |
| Proton Mail | Works |
| Fastmail | Works |
| Superhuman | Works |
Caveats (2)
- 1. Gmail: Observed 2026-10-28 (Emailens probe, Gmail web (Chrome), real-device run 1isFNBBaOyEo): Dropped, with flex-grow and flex-shrink beside it: the item sized to its content instead of 34%.
width:34%on the same item held. - 2. Yahoo Mail: Observed 2026-10-27 (Emailens probe, Yahoo Mail web (Chrome), real-device run E8fVpFwwLtL8): Dropped, with flex-grow and flex-shrink beside it: the item sized to its content instead of 34%.
width:34%on the same item held.
Caveats as recorded by caniemail (MIT), one entry per wording.
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fix
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