Outlook attachment size limit: which number applies to you

Which limit applies to you

• Outlook.com in a browser (personal Microsoft accounts: outlook.com, hotmail.com, live.com): 25 MB per email. Microsoft says this includes the message text as well as the attachments.
• Classic Outlook for Windows with an internet account (Outlook.com, Gmail or another POP/IMAP account): 20 MB of attachments in total. This is Outlook’s own default, set to stop it repeatedly trying to upload attachments most providers would refuse.
• Work accounts on Exchange: Microsoft’s Outlook help gives 10 MB as the default, but the real figure is whatever your organisation’s administrator has set, so it may be higher or lower.
• Outlook on a phone: Microsoft lists 33 MB as the maximum attachment for most account types, and 20 MB for iCloud accounts. The receiving server can still refuse a large message.

“The file you’re attaching is bigger than the server allows”

That is the message classic Outlook for Windows shows when the attachments pass its limit: 20 MB for internet accounts, or the size your Exchange administrator configured. It appears as you attach, before anything is sent.

For internet accounts, Microsoft documents a registry setting, MaximumAttachmentSize, that changes Outlook’s 20 MB check (for example, 30720 for 30 MB). It only changes Outlook’s own check: your email provider still applies its limit, so a 30 MB message to an Outlook.com mailbox can still be refused. Back up the registry before editing it, and on a work computer leave it to IT.

OneDrive links: Microsoft’s own workaround

In Outlook.com you can share a file from OneDrive instead of attaching a copy. Microsoft says links to OneDrive files don’t count toward the email size limit, and the linked file can be up to 2 GB. It uses your OneDrive storage, and the recipient needs permission to open the file.

Other ways to send a file that’s too big for Outlook

1. Make it smaller. Zipping, reduced-size PDF exports and lower-resolution video often get under 20 MB. See how to compress files for sharing.
2. Send a code in the email. Upload up to 500 MB to ShareQuik, then put the 8-character code in your Outlook message. No OneDrive storage is used and the recipient needs no Microsoft account.
3. Split it into several emails, each under the limit, if it’s a batch of separate files.

Sending from a work account? Check your organisation’s rules before using any outside service for company files. Approved storage is usually the right answer for anything confidential.