Outlook file size limit
What Outlook allows today, read on its own help page and dated, with the source so you can check it yourself.
- Accounts covered
- 3
- Last checked
- 30 September 2026
- Read on
- support.microsoft.com
| Account | Limit | Aim for | What it counts |
|---|---|---|---|
| Attachments | 25 MB | 18.1 MB | not stated by the platform |
| Work or school mailbox, default send limit (whole message) | 35 MB | 25.4 MB | the whole message, so the file has to be smaller than the number |
| Outlook for iOS and Android, whole message | 33 MB | 23.9 MB | the whole message, so the file has to be smaller than the number |
Outlook: Attachments
The page gives 25 MB for attached files and 2 GB for files shared from OneDrive. It states no separate limit for the whole message, and doesn't say whether the 25 MB counts the encoded message; we assume it does (see the encoding note on gmail-personal).
Checked 30 September 2026 on Sending limits in Outlook.com. Applies to any file type.
No earlier value is on record for this limit. That does not mean it never changed: we can only list changes we have seen.
Outlook: Work or school mailbox, default send limit (whole message)
The documented default maximum message size for Microsoft mailboxes is 35 MB for sending and 36 MB for receiving. Administrators can set anything from 1 MB to 150 MB, so an organisation may allow more or less (see exchange-admin-configured). Use the default unless you know the organisation's setting.
Checked 30 September 2026 on Exchange Online limits - Service Descriptions | Microsoft Learn. Applies to any file type.
No earlier value is on record for this limit. That does not mean it never changed: we can only list changes we have seen.
Outlook: Outlook for iOS and Android, whole message
Message size limit for the Outlook mobile apps, listed separately from desktop and lower than the 35 MB default. Microsoft's file attachment limit for mobile is 150 MB, but the mobile apps honour the lowest of the attachment, send and request size settings in the mailbox policy.
Checked 30 September 2026 on Exchange Online limits - Service Descriptions | Microsoft Learn. Applies to any file type.
No earlier value is on record for this limit. That does not mean it never changed: we can only list changes we have seen.