Email attachment limits are one of those technical constraints that catch people at the worst possible moments. Discovering that a file is too large to attach when you are trying to meet a deadline or respond to a time-sensitive request is avoidable if you know the limits in advance and have a workflow for files that exceed them.
Current limits by email provider (2026)
Gmail allows attachments up to 25MB per email. This limit applies to the total of all attachments in a single email, not per attachment. For files above 25MB, Gmail automatically converts the attachment to a Google Drive link if you try to attach it through the web interface. The recipient receives a link to the file in Drive rather than a downloaded attachment.
Outlook.com (Microsoft's consumer email service) allows attachments up to 20MB per email. Microsoft 365 accounts have the same 20MB limit by default, though Microsoft 365 administrators can configure higher limits for their organisation. The practical limit for sending to unknown corporate recipients is lower than 20MB because many corporate email servers set their own limits independently.
Apple iCloud Mail (the me.com and icloud.com services) limits attachments to 20MB when sending from the iCloud web interface. Apple's Mail Drop feature, which stores large files and sends a link instead, handles files up to 5GB and is automatically used when an attachment would exceed the limit.
Yahoo Mail allows attachments up to 25MB, matching Gmail's limit.
ProtonMail allows attachments up to 25MB per email for free accounts and up to 500MB (across multiple attachments) for paid accounts.
Zoho Mail allows 20MB for free accounts and up to 1GB for paid accounts, making it unusually generous for large file sharing via email.
Corporate email server limits
The limits above apply to consumer email services. Corporate email servers, including those running Microsoft Exchange or Google Workspace, often have independent limits configured by the organisation's IT department. These limits can be anywhere from 5MB to 50MB and are typically not advertised publicly.
If your email to a corporate recipient is rejected, the bounce message will usually indicate that the attachment was too large. If you are regularly sending large files to specific organisations, asking their IT department or your contact what the attachment limit is for their email system saves repeat rejections.
Many law firms and financial institutions set very low attachment limits (sometimes as low as 5MB) for security reasons. Legal documents, financial records, and confidential reports sent to these organisations should be compressed aggressively or shared through a secure file transfer service rather than email.
What happens when an attachment exceeds the limit
The outcome when an attachment exceeds the limit depends on the sending system. Gmail converts large attachments to Drive links automatically before the email is sent, so the sender may not realise the attachment was too large. The recipient receives a Drive link rather than a downloaded file.
Most other email systems reject the outgoing message entirely and send a bounce notification back to the sender explaining that the message was too large. The recipient never receives anything. This is the more common behaviour for Outlook and corporate email servers.
In rare cases, the receiving server rejects a message that the sending server accepted. The sender receives a delayed bounce notification hours or even days after sending, which creates the confusing situation of believing the email was delivered when it was not.
Reliable alternatives to large email attachments
Cloud storage links through Google Drive, OneDrive, Dropbox, or iCloud Drive are the most common replacement for large attachments. Upload the file to cloud storage, create a sharing link with the appropriate access level (view only for documents, full access for collaborative files), and paste the link in the email body. The recipient clicks the link to access the file without the attachment size limitation.
Secure file transfer services like WeTransfer (free up to 2GB), Smash (free up to 2GB), and similar services allow sending large files to recipients without requiring either party to have an account. The file is stored temporarily on the service's servers and the recipient downloads it through a link included in an automatically generated notification email.
Splitting a large PDF into multiple emails, each with one section of the document, is a lower-tech alternative that works when cloud services are not available or appropriate. Use Split PDF to divide the document into sections that each fit within the attachment limit, and send them in a numbered email sequence clearly indicating which section each email contains and how many total emails to expect.
Compressing files to meet attachment limits
For PDFs that are modestly above the attachment limit, compression is often the most straightforward solution. A PDF that is 28MB and needs to be under 25MB for Gmail can often be compressed to under 20MB with minimal quality impact. Use the PDF tools to compress and check the result size before attaching.
For images being sent as attachments, resizing to an appropriate display resolution and compressing as JPEG at 80 percent quality typically achieves file sizes well within any email attachment limit. A photo at 1200 pixels wide in JPEG format should be under 500KB in most cases.