Outlook Attachment Size Limit: What It Is and What to Do

Limits

The limit depends on the kind of account, and it counts the whole email, not only the file. These figures come from Microsoft's own pages, read on 23 October 2026 and checked again on 2 November.

Microsoft's guide to reducing attachment size gives 20 MB for internet email accounts, naming Outlook.com and Gmail, and 10 MB as the default for Exchange accounts. Its page on sending limits in Outlook.com says 25 MB for a file, with OneDrive attachments up to 2 GB. Those two pages disagree about Outlook.com, so we print both. For work and school accounts, the Exchange Online limits, updated 19 October 2026, give a default of 35 MB to send and 36 MB to receive, and let an administrator set anything from 1 MB to 150 MB.

Some websites give 34 MB for Outlook.com. We found no Microsoft page that says so, so we left it out.

Causes

A file well under the limit can still be refused, for three reasons.

• The limit counts the whole message, the text and every attachment together.
• A message grows in transit. Microsoft says messages routed outside its datacenters get an extra 33% from encoding, so a file close to the limit can still be refused.
• The person you send to has a limit too. A personal Gmail account takes 25 MB. The lowest limit along the way wins.

Built-In Fix

Microsoft's fix is to attach a link to the file instead of a copy. All four ways below are from Microsoft's pages on attaching files in Outlook and attaching files in Outlook for Mac.

Outlook on the web and Outlook.com

1. Create a new message, or reply or forward.
2. Select Attach file, then OneDrive.
3. Choose the file and select Next.

New Outlook for Windows

1. In a new message, select Attach File from the Insert group on the Message tab.
2. Choose a file under OneDrive. For a file on your computer, choose Browse This PC, select the down arrow beside the attachment and choose Upload to OneDrive.
3. Use the arrow beside the attachment name to choose who can view or edit it.

Classic Outlook for Windows

1. On the message tab, select Attach File from the Include group, then Browse Web Locations, then OneDrive.
2. Select the attachment link, then Manage access, to choose who can open it. You can also set an expiration date.

Outlook for Mac

1. In a new email, select Attach File.
2. Choose OneDrive to attach a file from your OneDrive, or choose Browse this Mac and then use the drop-down arrow beside the attachment to pick Upload to OneDrive.

Microsoft says that when you attach a OneDrive link, all recipients can view or edit the same file, and that a business account is set so everyone in your organization can edit it by default. Microsoft's Mac page said support for legacy Outlook for Mac would end in October 2026.

Link Options

OneDrive is the obvious choice because it is inside Outlook. Microsoft's own page names Dropbox, iCloud and Google Drive as the other popular choices, and the tools below all send a file as a link.

These are US dollars for one person, before tax, on the cheapest paid plan. OneDrive's free 5 GB is shared with the rest of your Microsoft account, including Outlook.com attachments, and Microsoft's Outlook.com page allows OneDrive attachments up to 2 GB a file. WeTransfer's free plan allows 10 transfers or 3 GB in any 30 days, and is for non-commercial use. Dropbox Plus is $9.99 a month billed yearly. OneDrive's price is from an archived US copy of 16 October, Google One's from 19 October and Dropbox's from 23 October. WeTransfer's price is from its US prices of 23 October.

Loop

Loop does not make Outlook accept a bigger attachment, and for one file sent once, OneDrive inside Outlook is simpler and free. Loop is a Mac app that turns a file into your own branded link, which you paste into your email. It is worth a look if you send big files often and want a few things OneDrive reserves for subscribers.

• A password and an expiry on the link. Microsoft says setting a password or an expiration date on a OneDrive link is only available to Microsoft 365 subscribers, on its OneDrive sharing page. In Loop they are settings on each link, with no separate plan.
• Your own storage. Files go into your own Cloudflare account, free up to 10 GB, so you do not share space with a 5 GB Microsoft account.
• A notification. Your Mac shows a notification the first time each reader's browser opens the file, and when it is downloaded, while Loop is running.

Loop costs $49 once, needs a Cloudflare account, runs on macOS 14 or later, and has no Outlook add-in that we found, so you copy the link and paste it into the message. We have not pasted a Loop link into Outlook, so we do not say how it looks there.

Raise the Limit

On a work or school account only your administrator can raise it, up to 150 MB. On Windows, Outlook's own cap on an internet account can be changed with a registry setting that Microsoft documents in its guide to this error. It changes only Outlook's cap, and your email service and the person you send to still apply theirs. We found no equivalent for the web or for Outlook for Mac.

Cost

Sending a large file can cost nothing. OneDrive is free up to 5 GB of storage, WeTransfer's free plan covers 3 GB in 30 days and Google gives 15 GB. Paid options start at $19.99 a year for OneDrive with 100 GB or for Google One with 100 GB. Loop is $49, paid once.

Loop's files are stored in your own Cloudflare account, free up to 10 GB. Past that, Cloudflare bills you. Cloudflare's pricing page, updated 30 October 2026, lists $0.015 per GB-month with no data-transfer charge for downloads, so 100 GB stored for a month is about $1.35 in storage after the free 10 GB. Cloudflare may also ask for a card when you switch storage on.

Loop includes a 14-day free trial that starts on first run, and Loop asks for no payment to begin it. During the trial a small "Shared with Loop" badge shows on the pages your clients see, and it goes with a licence.