Outlook’s attachment cap depends on which version you’re using: Outlook.com (web) allows 34 MB of files from your computer, while desktop Outlook defaults to 20 MB — though Microsoft 365 and Exchange Online mailboxes generally raise that to around 150 MB. This page gives the current numbers for Gmail and Outlook, then the part that explains the contradictions: what the email attachment file size limit is measured against, and which of the two servers in a delivery gets to enforce it. A known issue while sending files through email is the limit on the size of the attachments. Usually, any email service does not allow sending files larger than a few MB’s in size. Email attachment size limits are published as round numbers — 25MB for Gmail, 20MB for Outlook. Those numbers are real, but they are not the size of file you can actually attach. The usable limit is roughly a quarter smaller, for a reason that has nothing to do with your provider’s generosity. Most email providers cap attachments between 20 and 25 MB — and because attachments are Base64-encoded, the largest file you can actually send is about 75% of the stated limit. Here is every major provider, verified. Files over 25 MB auto-upload to Google Drive; recipients can receive up to 50 MB. A comprehensive reference for email attachment size limits across Gmail, Outlook, Yahoo, iCloud, and corporate Exchange servers. Learn practical techniques to compress and convert files to fit within limits — without losing quality. This reference table lists the current send and receive limits for major providers — and links to real sample files you can use to validate your app’s upload flow against each limit. Compare email attachment size limits across Gmail, Outlook, Yahoo, and Apple Mail. Learn why files bounce and how to send large files without email size caps. To help protect against abuse by spammers, Outlook.com limits the number of email messages that you can send in a single day, as well as the number of recipients for a single message. Outlook limits the size of files you can send. This limit prevents your computer from continually trying to upload very large attachments that exceed the limits of most internet service providers. For internet email accounts such as Outlook.com or Gmail, the email size limit is 20 megabytes (MB).