Email Attachment Size Limits: Complete Guide by Provider

Email attachment size limits are a daily frustration for millions of professionals. You finish a document, attach it to an email, and are greeted with an error message — or worse, your email sits in the outbox indefinitely without sending. Understanding the limits of each email provider and knowing your options for working around them is an essential modern productivity skill.

Email Attachment Size Limits by Provider

Gmail — 25 MB

Gmail allows attachments up to 25 MB. However, there is an important nuance: the 25 MB limit applies to the total message size after encoding. Email attachments are encoded using Base64, which increases the file size by approximately 33%. This means your actual file can be no larger than about 18–20 MB before encoding. If your file exceeds this, Gmail automatically provides a Google Drive link option instead.

Outlook / Microsoft 365 — 20 MB to 150 MB

Outlook.com (free) has a 20 MB attachment limit. Microsoft Business plans have a default limit of 25 MB, but administrators can increase this up to 150 MB using Exchange Online settings. Even with the higher limit, users may experience issues if the recipient's server has a lower limit. For files over 20 MB, Outlook also offers OneDrive integration for sharing via link.

Yahoo Mail — 25 MB

Yahoo Mail allows attachments up to 25 MB. Yahoo also counts attachments against your total storage quota, so large attachments can fill up your mailbox quickly. Yahoo recommends using their cloud storage or third-party services for larger files.

ProtonMail — 25 MB

ProtonMail has a 25 MB limit. However, because ProtonMail encrypts your emails, the encryption overhead means your actual file size limit may be lower — around 15–20 MB for the file itself. ProtonMail offers a file sharing feature for larger files with end-to-end encryption.

iCloud Mail — 20 MB

iCloud Mail has a 20 MB attachment limit. Like other providers, iCloud Mail integrates with iCloud Drive, allowing you to share large files via links instead.

How to Compress Files for Email Attachments

When your files are too large for your email provider's limit, compression is the first solution to try. Here are the most effective strategies:

Compress PDF Files

PDF files can often be reduced by 50–90% using compression tools. The 8era PDF Compressor offers two modes: By Size lets you target a specific output size (e.g., "make this PDF under 10 MB"), while By Quality lets you control the trade-off between file size and image quality. For document PDFs (mostly text), even high compression ratios produce excellent results. For scanned documents with embedded images, moderate compression preserves readability while significantly reducing size.

Compress Images

Before attaching images to an email, compress them. The 8era Image Compressor can reduce JPEG and PNG file sizes by up to 80% with minimal visible quality loss. For email, images at 70–80% quality are practically indistinguishable from originals but a fraction of the size. Converting multiple images into a single PDF and then compressing that PDF can also save significant space.

Choose the Right Format

• Use JPEG instead of PNG for photographs (JPEG is 5–10× smaller)
• Use WebP for even smaller file sizes (compatible with most modern email clients)
• Convert Word/Excel files to PDF before sending (PDF is often smaller and more reliable)
• Zip multiple files together, then compress the archive if needed

Alternatives to Email Attachments

When compression is not enough, or you need to send files larger than 50 MB, use one of these alternatives:

• Cloud storage links: Google Drive, Dropbox, OneDrive, and iCloud Drive all generate shareable links. You control access and expiration. Recipients download the original file without email size limits.
• Temporary file sharing: Services like WeTransfer (free up to 2 GB) and Firefox Send let you upload a file and generate a time-limited download link. Files are automatically deleted after a set period.
• Enterprise solutions: For businesses, SharePoint, Box, and Egnyte provide secure file sharing with audit trails, version history, and granular permission controls.

Conclusion

Email attachment limits are a practical constraint that every professional encounters. Understanding your provider's limit — and knowing that the real limit is lower after encoding overhead — helps you plan ahead. Compression tools like 8era's PDF and image compressors can dramatically reduce file sizes, often bringing them within attachment limits. For larger files, cloud storage links and dedicated file sharing services offer reliable alternatives. By combining compression with the right sharing method, you can send any file, any size, to anyone.