Outlook attachment size limit (2026) and how to send bigger files
Outlook's real attachment limits, explained
Outlook's attachment size limit is 25 MB per message on Outlook.com, a default of 35 MB to send on Microsoft 365 work accounts (an admin can raise it to 150 MB), and 20 MB by default in Outlook for Windows for POP and IMAP accounts. Because email encoding adds about a third to every file, the real ceiling is lower than the number on the page. For anything bigger, send a link: a OneDrive link, or a Link in Seconds link that opens in any browser with no sign-in.
At a glance
- Outlook.com (free)
- 25 MB per email, text and attachments together
- Microsoft 365 work
- 35 MB send, 36 MB receive by default; up to 150 MB
- Outlook for Windows, POP/IMAP
- 20 MB default
- Usual error
- "Bigger than the server allows"
- Microsoft's fix
- Share a OneDrive link instead
- Link option
- Free account, up to 250 MB per file, no sign-in to view
What is the Outlook attachment size limit in 2026?
“Outlook” is three different things, and each has its own limit. The one that stops you is whichever is lowest between your account, your Outlook app and the recipient's server.
| Where you send from | Limit Microsoft documents | Who sets it |
|---|---|---|
| Outlook.com, Hotmail, Live (personal) | 25 MB per email, including text | Microsoft, fixed |
| Microsoft 365 / Exchange Online (work, school) | 35 MB send, 36 MB receive by default | Your admin, from 1 MB up to 150 MB |
| Microsoft 365 mail leaving Microsoft | About 112 MB at the 150 MB maximum | Encoding overhead |
| Outlook for Windows, POP or IMAP account | 20 MB default | The Outlook app (registry) |
| Outlook for Windows, older Exchange servers | Often 10 MB | The Exchange admin |
| OneDrive link from Outlook.com | 2 GB per file | Microsoft |
Outlook.com
Microsoft's Outlook.com pages put the cap at 25 MB for the whole email, text included, and there is no setting to raise it. Attachments you keep also count toward the free 5 GB of Microsoft cloud storage, shared with OneDrive. Fill that up and Outlook.com stops sending and receiving mail.
Microsoft 365 and Exchange Online
Work and school mailboxes default to 35 MB to send and 36 MB to receive. Admins can set any limit from 1 MB to 150 MB. Microsoft notes that messages leaving its datacenters grow by about 33% from encoding, so even at the 150 MB maximum, mail to outside addresses tops out around 112 MB. If a colleague can send you 40 MB but a client can't, that's the reason: their admin picked a lower number.
Outlook desktop
Outlook for Windows adds a limit of its own for internet accounts (POP3, IMAP): 20 MB across all attachments by default. Microsoft documents a MaximumAttachmentSize registry value to change it, but raising it on your PC doesn't raise your email provider's server limit, so the message can still bounce. With an Exchange account, the limit comes from the server's maximum send size instead.
What do Outlook's size errors mean?
- “The file you're attaching is bigger than the server allows. Try putting the file in a shared location and sending a link instead.” Your mailbox's send limit is lower than the attachment. On a work account, only your admin can change it.
- “Attachment size exceeds the allowable limit.” Outlook for Windows hit its own client limit, usually the 20 MB default for a POP or IMAP account.
- A bounce saying the message is too large. Your Outlook sent it, but the recipient's server refused it. Nothing you change on your side will fix that one.
Does sending a OneDrive link fix it?
Usually. Microsoft's advice is to upload the file to OneDrive and share a link, and links don't count toward the email size limit. In Outlook you can attach from cloud locations or choose to upload and share, and Outlook.com links can point to files up to 2 GB. The catches are the same as with any drive:
- Permissions. If the link is set to specific people, recipients may have to sign in with a Microsoft account, or wait for you to grant access.
- Company rules. Many work tenants restrict sharing with people outside the organization, so a client can't open the link at all.
- Storage. On a free account, the file eats into the same 5 GB that holds your Outlook.com attachments.
How do I send a large file from Outlook as a plain link?
If you'd rather not deal with OneDrive permissions, upload the file somewhere that gives you a link anyone can open, and paste it into your email.
- 1
Upload the file to Link in Seconds
Sign in with a free account and drop the file in. Free files can be up to 250 MB each. - 2
Copy the link
The link opens the file in any browser. Your recipient needs no Microsoft account, no OneDrive and no sign-in. - 3
Paste it into your Outlook message
The link adds almost nothing to the message size, so no Outlook limit or receiving server can bounce it. - 4
See when it was opened
The link's analytics show views and visitors. Replace the file later and the same link shows the new version.
Every link feature is free on every plan, including a password, an expiry date, a view limit, view-only mode and a QR code. Links never expire unless you set a date. Free accounts get 50 live links and 500 MB of storage with files up to 250 MB; Pro takes files up to 500 MB. For files of several gigabytes, OneDrive or a dedicated transfer service handles more than we do.
OneDrive link vs a Link in Seconds link
| OneDrive link | Link in Seconds | |
|---|---|---|
| Built into Outlook | Yes | No, paste the link |
| Recipient sign-in | Sometimes, depends on sharing | Never |
| Subject to your tenant's sharing rules | Yes | No |
| See if it was opened | Not on personal accounts | Yes, view count and analytics |
| Largest file | 2 GB from Outlook.com | 250 MB free, 500 MB on Pro |
| Password, expiry, view limit | Depends on plan | Yes, free |
Quick answers
What is the attachment size limit in Outlook?
It depends on the account. Outlook.com allows 25 MB per email including text and attachments. Microsoft 365 work mailboxes on Exchange Online default to 35 MB to send and 36 MB to receive, and an admin can raise that to 150 MB. Outlook for Windows also applies its own 20 MB default to POP and IMAP accounts.
Why does Outlook say the file is bigger than the server allows?
The message is over the limit set by your mail server or your Exchange admin. Base64 encoding adds about a third to every attachment, so a file that looks under the limit can still be over it. Microsoft's own fix is to put the file in a shared location and send a link.
Can I increase the Outlook attachment limit?
For Microsoft 365 work accounts, only your admin can, up to 150 MB. For POP or IMAP accounts in Outlook for Windows, Microsoft documents a MaximumAttachmentSize registry setting, but your email provider's server limit still applies. Outlook.com's 25 MB is set by Microsoft, with no setting to raise it.
How do I send a file larger than 25 MB in Outlook?
Share it as a link. Outlook offers OneDrive links, which allow files up to 2 GB from Outlook.com. Or upload it to Link in Seconds (up to 250 MB on the free plan) and paste the link, which opens in any browser with no account needed to view and shows a view count.
Does a OneDrive link count toward the Outlook size limit?
No. Microsoft says links to OneDrive files don't count toward the email size limit. The file does count toward your Microsoft cloud storage, which is 5 GB on a free account and is shared with Outlook.com attachments.
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