Email File Size Limit: Provider Caps and How to Send Large Files

You can send about 20 to 25 MB in an email on most providers, and because Base64 encoding inflates a file by roughly 33%, the safe target is to keep the whole message under 10 MB. There is no minimum size, so the maximum is the only limit worth planning around. Anything over 10 MB should go as a cloud link through Google Drive, OneDrive, or Dropbox rather than as an attachment, which also sidesteps the recipient's own size cap.

Every provider caps how much you can send, and the real ceiling is lower than the number they advertise. Here is what each major service allows, why your file is bigger than it looks once it leaves your outbox, and what to do when you need to move something large.

Email file size limits by provider

Most email providers cap a single message at 20 to 25 MB, and the cap covers the whole message, not just the attachment. Gmail, Outlook.com, and Yahoo Mail all sit at 25 MB outgoing. Apple iCloud Mail and Zoho Mail cap at 20 MB, and ProtonMail splits its cap by direction. Corporate Exchange is usually the tightest, because the cap is whatever your administrator set and the default Microsoft documents for Exchange Server is only 10 MB. Every figure in the table below is fetched directly from the provider's own published help page; the source URL is named in the third column so you can check it yourself.

Provider	Published message size limit	Where the figure comes from
Gmail (personal accounts)	25 MB	Google's Gmail attachment help page, linked later in this article. Files over 25 MB auto-upload to Google Drive as a link
Google Workspace	Set by your administrator	The same Google help page states that for work and school accounts the administrator sets both the sending and the receiving limit
Outlook.com	25 MB	Microsoft, "Sending limits in Outlook.com" (support.microsoft.com/en-us/office/sending-limits-in-outlook-com-279ee200-594c-40f0-9ec8-bb6af7735c2e). Share via OneDrive for files up to 2 GB, per the same page
Microsoft 365 / Exchange Online	35 MB sending, 36 MB receiving by default, administrator-configurable up to 150 MB	Microsoft, "Exchange Online limits" (learn.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/exchange-online-limits)
Exchange Server (on premises)	10 MB by default, administrator-configurable	Microsoft's Exchange Server message size limits page, linked in the next section, lists a 10 MB default for both maximum send and maximum receive size
Yahoo Mail	25 MB	Yahoo, "Message size limits in Yahoo Mail" (help.yahoo.com/kb/SLN5673.html): the sum of all attachments in one message must not exceed 25 MB
Apple iCloud Mail	20 MB	Apple Support, "Mailbox size and message sending limits in iCloud" (support.apple.com/en-us/102198). Turning on Mail Drop raises this to 5 GB via an expiring link
ProtonMail	50 MB incoming, 25 MB outgoing	Proton Support, "Attachment and email size limits" (proton.me/support/attaching-multiple-documents-to-a-message), which states the two directions separately rather than one shared cap
Zoho Mail	20 MB for personal accounts	Zoho, "Attachments in Emails" (zoho.com/mail/help/attachments.html), which also notes that an organization's administrator can restrict it further

AOL Mail is left out of this table: no AOL help page currently states a published attachment size limit, so a specific figure for AOL cannot be verified against a primary source. Third-party guides commonly repeat 25 MB, but that number traces to no official AOL documentation.

Two things matter more than any single number here. First, the cap applies to your entire message, including the body text, your signature, and any inline images, not just the file you attached. Second, the most restrictive limit wins, a rule Microsoft's Exchange documentation states explicitly: a message has to fit inside the sender's limit and the recipient's limit, so a file you can send may still bounce off a recipient whose server caps incoming mail lower than yours does.

On Microsoft 365 and Exchange Server, the number you actually get is often whatever your administrator set, though Microsoft 365 ships with a default of 35 MB sending and 36 MB receiving until an admin changes it. Microsoft's documentation notes that administrators can let specific mailboxes send and receive larger messages than the rest of the organization, but that the organizational limit still applies to mail crossing the internet, so how many MB you can send often comes down to your own IT policy rather than a published ceiling.

Why a 25 MB file isn't really 25 MB

A 25 MB limit does not mean you can attach a 25 MB file. Providers measure the encoded size of the message, and Base64 encoding adds roughly 33% to every attachment. A 20 MB file becomes about 27 MB on the wire, a 15 MB file becomes about 20 MB, and a 10 MB file arrives weighing around 13.3 MB. The usable ceiling is therefore roughly 75% of the published one, which is about 18 MB of raw file against a 25 MB cap.

When you attach a file, your provider does not send it as-is. It encodes the file into plain text (a format called Base64) so it can travel safely through the mail system, and that encoding adds roughly 33% to the size. Microsoft's own worked example on that page makes the gap concrete: configure a 64 MB maximum message size and the realistic maximum you actually get is about 48 MB.

That is why a 24 MB file can bounce off a 25 MB limit: the cap measures the encoded size, not the file sitting on your hard drive. The practical answer to how many MB you can attach is therefore well below the headline figure, and it drops further once the message body, your signature, and any inline images are counted against the same cap.

The different kinds of email size limit

"Email file size limit" covers four separate ceilings, and any one of them can stop your message: your provider's sending limit, a per-file attachment cap, the recipient server's receiving limit, and the recipient's mailbox storage quota. The four are set independently, so clearing your own limit is no guarantee the message lands.

• Sending limit: the total outgoing message size your provider allows, usually 10 to 25 MB including encoding overhead.
• Per-file attachment cap: some platforms limit each individual file separately from the whole message, so a message can pass the total-size check while one oversized file inside it does not.
• Receiving limit: the recipient's mail server sets its own ceiling on incoming messages, independent of yours.
• Mailbox storage: a recipient whose mailbox is full can reject your message even when it is well within the size limit, often with no warning to you.

What happens when an email is too big

An oversized email fails in one of five ways: an immediate bounce from your own provider, a delayed rejection from the recipient's server, a silent drop with no bounce at all, attachment stripping that delivers the body without the file, or spam-folder placement. Only the first two reliably tell you the message did not arrive.

• An immediate bounce: your provider rejects the message before it leaves, often with a 552 error that says the size exceeds the maximum allowed.
• A delayed rejection: your provider accepts the send, then the recipient's server bounces it back minutes later with a non-delivery report.
• A silent drop: some older corporate servers accept the message and never deliver it, with no bounce at all, so you assume it landed.
• Attachment stripping: a corporate filter removes the oversized file and delivers the body alone, sometimes with a note and sometimes without.
• The spam folder: an unusually large or oddly structured message can look suspicious to filters and land in spam even when it is technically under the cap.

How to send a file that's too large

To send a file that exceeds the limit, share a link instead of an attachment. Upload the file to Google Drive, OneDrive, or Dropbox and paste the share link, or let Gmail and Outlook swap the attachment for a cloud link automatically. Per Microsoft's Outlook.com sending-limits page (support.microsoft.com/en-us/office/sending-limits-in-outlook-com-279ee200-594c-40f0-9ec8-bb6af7735c2e), a OneDrive link carries files up to 2 GB. Compressing the file is a fallback, not a fix.

• Let your provider do it: Gmail automatically uploads anything over 25 MB to Google Drive and inserts a share link, and Outlook does the same through OneDrive.
• Upload to cloud storage yourself: drop the file in Google Drive, OneDrive, or Dropbox, set who is allowed to open it, and paste the link. You can revoke access later if you sent the wrong version.
• Use OneDrive for very large files: a OneDrive share link can handle a file up to 2 GB, far beyond any attachment cap.
• Compress first if you must attach: zip non-image documents, resize images before attaching, or re-export a PDF at web quality to drop it under the limit. Zipping images barely helps, since JPEGs and PNGs are already compressed, and some spam filters treat ZIP files as suspicious, so only zip when it saves real space and the recipient expects it.

What attachment size is actually safe to send

The safe attachment size is anything that keeps the raw file, before encoding, under about 7.5 MB, which encodes to roughly 10 MB and clears almost every corporate cap. Files under 1 MB sit far below every limit in the table above. Between 5 and 10 MB of raw file, test the send first. Above 10 MB of raw file, send a link every time. The bands below are a working rule of thumb derived from the caps in that table plus the 33% encoding overhead, not thresholds any provider publishes.

Raw file size (before encoding)	What to do	Why
Under 1 MB	Attach it	Far below every published limit above, even after the 33% encoding overhead
1 to 5 MB	Attach it	5 MB encodes to about 6.7 MB, still under the lowest limit in the table
5 to 10 MB	Attach with caution, test first	Send it to yourself, then open the message properties to read its true total size
Over 10 MB	Send a link	10 MB encodes to about 13.3 MB, which exceeds the 10 MB default Microsoft documents for Exchange Server

How oversized emails hurt deliverability

Oversized emails are a deliverability problem, not just an inbox annoyance. Repeatedly sending messages that bounce on size drags down your sender reputation over time, and large or oddly structured emails are more likely to trip spam filters. Both feed into your overall email deliverability, and attachment bloat sits alongside the usual causes of a climbing bounce rate.

Size is one of two bounce sources you control before a send. The other is the list itself: invalid addresses hard-bounce no matter how small the message is. It only takes a moment to check an address before you send, and BounceCheck is an email verification tool that checks each address in real time and removes the invalid ones before you send, so run your list through BounceCheck before your next campaign.

FAQs about sending large files

How many MB can you send in an email?

About 20 to 25 MB on most providers, measured across the whole message rather than the attachment alone. Gmail, Outlook.com, and Yahoo Mail cap at 25 MB, Apple iCloud Mail and Zoho Mail at 20 MB. Because Base64 encoding adds roughly 33%, the usable figure is about 18 MB of raw file against a 25 MB cap, and less once your signature and inline images are counted.

How do I email a file larger than 25 MB?

Do not attach it. Upload the file to Google Drive, OneDrive, or Dropbox and share a link, or let Gmail and Outlook do it for you, since both swap an oversized attachment for a cloud link automatically. A link also sidesteps the recipient's own size cap.

How many MB is too big for email?

Anything over about 10 MB for the whole message is risky. The published caps are usually 20 to 25 MB, but encoding overhead and tighter recipient limits mean 10 MB is the safe target. Above that, send a link.

Is there a minimum file size for email?

There is no minimum. Email has no floor on message size: a plain text message with no attachment is only as large as its headers and text, which is negligible against any provider cap. Attachments and inline images are what push a message toward the ceiling, so the maximum is the only limit worth planning around.

Why did my 24 MB attachment bounce when the limit is 25 MB?

Because the cap measures the encoded size, not the raw file. A 24 MB file becomes roughly 32 MB after Base64 encoding, which exceeds Gmail's 25 MB ceiling. Keep the raw file at about 75% of the published limit, so under roughly 18 MB on a 25 MB cap, and it will send.

Can I send a 100 MB file by email?

Not as an attachment. No mainstream provider accepts a 100 MB attachment. Upload it to cloud storage and share a link instead, or use a file-transfer service. A OneDrive link can handle files up to 2 GB.

How do I send a file over 25 MB in Outlook?

Upload it to OneDrive and insert a share link rather than attaching it. Outlook's OneDrive attachment limit is 2 GB, so the recipient gets a link and can even collaborate on the file in real time.