What is the maximum email attachment size for Gmail?

Gmail allows attachments up to 25 MB when sending and can receive attachments up to 50 MB. However, due to Base64 encoding overhead, the actual file size limit when sending is approximately 18-19 MB. Files larger than 25 MB are automatically uploaded to Google Drive and shared as a link.

Why is my 20 MB file rejected when the limit is 25 MB?

Email attachments are encoded using Base64, which increases the file size by approximately 33%. A 20 MB file becomes roughly 26.6 MB after encoding, which exceeds the 25 MB limit. To stay safe, keep files under 18 MB for a 25 MB limit, or compress the file before attaching.

How can I send a file that is too large for email?

You have several options: compress the file using a PDF compressor or image compressor to reduce its size, split a large PDF into smaller parts, upload to Google Drive, Dropbox, or OneDrive and share a link, or use the platform's built-in large file feature like Gmail's Google Drive integration or Apple Mail Drop.

Does the attachment limit apply to total attachments or per file?

The limit applies to the total size of all attachments combined in a single email, not per file. If Gmail's limit is 25 MB, you cannot attach five 10 MB files — the total would be 50 MB, which exceeds the limit. You would need to send multiple emails or compress the files.

What is Apple Mail Drop and how does it work?

Apple Mail Drop is a feature in Apple Mail that automatically uploads large attachments (up to 5 GB) to iCloud and sends the recipient a download link. It activates automatically when your attachment exceeds the 20 MB limit. Recipients have 30 days to download the file, and it works even if they do not use Apple Mail.

Email Attachment Size Limits by Provider (2026): Gmail, Outlook, Yahoo & More

The complete reference table — plus how to send files that are too large

By Ben Praveen J · March 24, 2026

You have a file to email. The send button is right there. But the email bounces back: "attachment too large." Every email provider has a size limit, and they are all different. Worse, the actual limit is smaller than advertised because of how email encodes attachments.

This guide gives you every provider's limit in one table, explains why your file gets rejected even when it seems small enough, and shows you how to get around the limits.

Email Attachment Limits: The Master Table

This table shows the maximum attachment size for every major email provider as of 2026. The "Effective Limit" column shows the real-world maximum file size after accounting for Base64 encoding overhead.

Email Provider	Stated Limit	Effective Limit*	Large File Feature
Gmail	25 MB send / 50 MB receive	~18 MB	Google Drive (up to 15 GB)
Outlook.com (Hotmail)	20 MB	~15 MB	OneDrive (up to 2 GB link)
Outlook Desktop (Exchange Online)	150 MB (default)	~112 MB	OneDrive integration
Outlook Desktop (Exchange On-Prem)	10-150 MB (admin setting)	75% of stated	Depends on config
Yahoo Mail	25 MB	~18 MB	None built-in
Apple iCloud Mail	20 MB	~15 MB	Mail Drop (up to 5 GB)
ProtonMail	25 MB	~18 MB	None built-in
Zoho Mail (Free)	20 MB	~15 MB	Zoho WorkDrive link
Zoho Mail (Paid)	40 MB	~30 MB	Zoho WorkDrive link
AOL Mail	25 MB	~18 MB	None built-in
GMX Mail	50 MB	~37 MB	GMX Cloud link
Tutanota (Tuta)	25 MB	~18 MB	None built-in
Corporate Exchange	Typically 10-35 MB	75% of stated	Varies by organization
Government (.gov)	Often 10-15 MB	~7-11 MB	Usually none

*Effective Limit accounts for ~33% Base64 encoding overhead. Your actual file must be under this size.

Why the Real Limit Is Smaller Than Advertised

When you attach a file to an email, the email system does not send the raw file. It converts the attachment into text using Base64 encoding, which is a way of representing binary data (images, PDFs, documents) as plain text characters that can safely travel through email servers.

Base64 encoding increases the data size by approximately 33%. That means:

A 25 MB limit (Gmail, Yahoo, ProtonMail) really means your file can be about 18-19 MB
A 20 MB limit (Outlook.com, iCloud, Zoho Free) really means about 15 MB
A 10 MB limit (some corporate servers) really means about 7.5 MB

This is why a 20 MB PDF gets rejected by Gmail even though the stated limit is 25 MB. After Base64 encoding, that 20 MB file becomes approximately 26.6 MB — over the limit.

Additional overhead factors

Base64 is the biggest factor, but there are others:

MIME headers: Each attachment has metadata (filename, content type) that adds a few kilobytes.
Multiple attachments: The limit applies to the total of all attachments, not per file. Five 4 MB files equal 20 MB before encoding — about 26.6 MB after.
Email body: The text and HTML of your email body also count toward the total message size, though this is usually negligible (a few KB).

What to Do When Your File Is Too Large

Option 1: Compress the file

The fastest solution. Compression can dramatically reduce file size without meaningful quality loss:

PDF files: Compress PDF — reduces most PDFs by 50-80%. A 25 MB scanned document can drop to 5-8 MB.
Images: Compress Images — reduces JPEG and PNG files by 40-80% while looking identical.
Multiple images: Compress each image individually before attaching. A folder of 15 photos at 3 MB each (45 MB total) can compress to 15 MB total.

Need to email a PDF? Compress your PDF first — most PDFs shrink by 50-80%. Free, instant, no signup.

Option 2: Split the file

If compression alone is not enough, split the document:

Split a PDF into multiple smaller PDFs using PDF Split. Send each part as a separate email.
Split a batch of images across multiple emails — for example, 5 images per email instead of 20.

Option 3: Use cloud storage links

Upload to a cloud service and share a download link instead:

Google Drive: Up to 15 GB free storage. Gmail automatically offers to upload large files to Drive.
OneDrive: 5 GB free. Outlook integrates directly — click the cloud icon when attaching.
Dropbox: 2 GB free. Share a link that anyone can download from.
iCloud: Apple Mail Drop activates automatically for files over 20 MB, supporting up to 5 GB. Recipients have 30 days to download.

Platform-Specific Tips

Gmail

Gmail handles large files gracefully. When you try to attach a file over 25 MB, Gmail automatically offers to upload it to Google Drive and insert a sharing link instead. The recipient gets a link to view or download the file. The link inherits your sharing settings — you can allow anyone with the link, or restrict to specific people.

Pro tip: If you receive a "file too large" error for a file under 25 MB, it is because of Base64 encoding. Compress the file to under 18 MB and try again.

Outlook

Outlook.com (the web version) has a 20 MB limit, while Outlook desktop with Exchange Online defaults to 150 MB. The desktop app integrates with OneDrive — when you attach a large file stored in OneDrive, it sends a link instead of the actual file. This also means the recipient always gets the latest version if you update the file after sending.

Corporate Outlook users: Your IT administrator controls the attachment limit. If you are hitting a wall at 10 or 25 MB, ask your IT team about the configured limit. Some organizations set it as low as 10 MB to conserve server storage.

Apple Mail

Apple Mail has a 20 MB attachment limit, but Mail Drop makes this a non-issue for Apple users. When your attachment exceeds 20 MB, Mail activates Mail Drop automatically, uploading the file to iCloud (up to 5 GB). The recipient receives a download link that works for 30 days. Mail Drop does not count against your iCloud storage quota.

Important: Mail Drop only works when sending from Apple Mail. If you access iCloud Mail through a web browser, the 20 MB limit applies without Mail Drop.

ProtonMail

ProtonMail's 25 MB limit applies to encrypted and unencrypted emails alike. ProtonMail does not have a built-in large file sharing feature. For files exceeding the limit, compress first or use an external cloud service. Note that if you are sending encrypted email, the recipient must be a ProtonMail user or use the provided link to decrypt — cloud storage links bypass this encryption.

Quick Reference: Safe Sizes by Provider

To avoid any issues, keep your total attachment size under these safe thresholds:

If your recipient uses...	Keep total attachments under
Gmail	18 MB
Outlook.com / Hotmail	15 MB
Yahoo Mail	18 MB
Apple iCloud Mail	15 MB
Corporate email (unknown)	7 MB (safest)
Government email	7 MB (safest)
Unknown provider	10 MB (safest)

When you do not know what email provider the recipient uses, 10 MB is the safest maximum. This works with virtually every email system in existence, including restrictive corporate and government servers.

How to Quickly Reduce File Size for Email

Here is a quick decision tree:

Is it a PDF? Compress it. Scanned PDFs shrink 70-90%. Image-heavy PDFs shrink 50-75%.
Still too large? Split the PDF into smaller sections and send multiple emails.
Is it images? Compress them. Most photos shrink 50-80% without visible quality loss.
Is it a video? Do not email video. Upload to Google Drive, Dropbox, or OneDrive and share a link. Video files are almost always too large for email.
Multiple small files? ZIP them into one archive, then check if the ZIP is under the limit.

FAQ

What is the maximum email attachment size for Gmail?: Gmail allows attachments up to 25 MB when sending and can receive attachments up to 50 MB. However, due to Base64 encoding overhead of approximately 33%, the actual file you attach should be under 18-19 MB. Files larger than 25 MB are automatically uploaded to Google Drive and shared as a download link.
Why is my 20 MB file rejected when the limit is 25 MB?: Email attachments are encoded using Base64, which increases the data size by approximately 33%. A 20 MB file becomes roughly 26.6 MB after encoding, exceeding the 25 MB limit. To stay safe, keep files under 18 MB for a 25 MB provider limit. Compress your file to reduce it below the threshold.
How can I send a file that is too large for email?: You have several options: compress the file using a PDF compressor or image compressor to reduce its size, split a large PDF into smaller parts and send multiple emails, upload to Google Drive, Dropbox, or OneDrive and share a link, or use your email platform's built-in large file feature like Gmail's Drive integration or Apple Mail Drop.
Does the attachment limit apply to total attachments or per file?: The limit applies to the total size of all attachments combined in a single email, not per individual file. If your provider's limit is 25 MB, attaching five 4 MB files uses 20 MB of your allowance — which becomes about 26.6 MB after encoding, exceeding the limit. You would need to split attachments across multiple emails or compress them.
What is Apple Mail Drop and how does it work?: Apple Mail Drop automatically uploads large attachments (up to 5 GB) to iCloud when they exceed the 20 MB email limit. The recipient receives a download link instead of the actual file and has 30 days to download it. Mail Drop works even if the recipient does not use Apple Mail. It does not count against your iCloud storage quota. However, it only works when sending from the Apple Mail app — not iCloud Mail in a browser.

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