Attachment size limits, in one screen
Every published attachment limit describes the finished message, not the file sitting on your desk. The file gets larger on the way out, and the number that decides acceptance belongs to the recipient’s server, not to yours.
| Personal Gmail | 25 MB per message, sending |
| Google Workspace | Set by the administrator; Enterprise Plus sends 50 MB and receives 70 MB since February 2026 |
| Microsoft 365 | 35 MB sending and 36 MB receiving by default, configurable from 1 MB to 150 MB |
| Encoding cost | Base64 turns 3 bytes into 4 characters, so a 20 MB file travels as roughly 27 MB |
| What actually rejects | The SIZE value the receiving server advertises, answered with a 552 or a 452 |
The gmail limit on attachment size is the most searched number in email, and on its own it predicts almost nothing. Gmail accepts a 24 MB file and the message still bounces. A colleague on Microsoft 365 sends a 30 MB deck to one recipient and it arrives, sends the same deck to another and it does not. Neither case is a bug.
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.
The limit applies to the encoded message, not to your file
An attachment cannot travel as raw bytes. SMTP was specified for 7-bit text, so binary files are re-encoded into printable characters before transmission, almost always with base64, which is one of the encodings defined by the MIME specifications. Our reference on how MIME structures a message into parts and encodings covers the mechanism.
The arithmetic is what matters. Base64 represents every 3 bytes of input as 4 output characters, an increase of one third before anything else is counted. Add a line break every 76 characters, the MIME part headers, the boundary strings and the message headers, and real growth lands slightly above that.
Both large providers publish their own figure for this. Microsoft states that messages routed outside its datacenters are subject to “an additional 33% translation encoding increase”. Google is blunter in its Workspace documentation: the receiving limits it publishes “are the limit after encoding, which adds about a 37% increase”.
So the practical rule for a strict 25 MB ceiling is to keep the files themselves under about 18 to 20 MB. That gap, not any hidden policy, is why a 24 MB file fails a 25 MB limit. If you want a single number for the maximum email attachment size that is safe almost everywhere in 2026, it is closer to 10 MB of actual files than to any published ceiling.
Gmail attachment size limits
Personal accounts
Google’s own support page is unambiguous: “For personal Gmail accounts, the limit is 25 MB.” That figure is combined across all files in the message, not per file, and it is a sending limit.
Above it, Gmail does not refuse the message. Google describes the behavior plainly: “If your total attachment size is greater than the limit, Gmail automatically removes the attachment and adds it as a Google Drive link in the email.” Most people who believe they have sent a 60 MB attachment through Gmail have sent a link, with whatever sharing permissions came with it.
Google Workspace accounts
For work and school accounts, Google states that “your Google Workspace administrator sets the attachment sending limits and attachment receiving limits”. There is no single Workspace number to quote, which is why a colleague’s experience is not evidence about your own account.
One edition changed recently and it is worth knowing about. In a Workspace update dated 24 February 2026, Google raised the Enterprise Plus sending limit to 50 MB, “doubling the previous 25MB limit”, and increased the incoming message size limit for that edition to 70 MB. Gmail receiving limits sit at 50 MB for Enterprise Standard and 70 MB for Enterprise Plus, and Google notes that these are the post-encoding values. A single message can carry up to 500 attachments on the receiving side.
Two things people expect that are not true
There is no 5 MB tier in Gmail. The recurring search for a gmail attachment size limit 5mb comes from corporate mail gateways and from older mail clients that impose their own cap, not from Gmail. The gmail attachment size limit android is the same 25 MB as the desktop web client, because the limit lives with the account, not with the app.
And the limit cannot be raised on a personal account. Searches for a gmail attachment size limit increase have one honest answer for consumer accounts: no, and the workaround is the Drive link Gmail already substitutes.
Outlook and Microsoft 365 attachment size limits
The email attachment size limit outlook question has more than one answer, because Microsoft applies a mailbox limit and a client limit, and the smaller of the two wins.
The mailbox side, from the Exchange Online service description: “The default maximum message size for Microsoft mailboxes is 35 MB for sending and 36 MB for receiving”, and administrators “can specify a custom limit between 1 MB and 150 MB”. The asymmetry is deliberate, so that a message sent at the ceiling still fits on arrival.
The client side is where the outlook mail attachment size limit diverges by app:
- Outlook for Windows and for Mac: up to 150 MB per attachment
- Outlook on the web: up to 112 MB, because it accounts for the 33% encoding overhead and restricts what you can send to 25% below the configured setting
- Outlook for iOS and Android: 33 MB
- Any message: a maximum of 250 attachments
Those client ceilings only apply if the mailbox policy allows them, which by default it does not. With the default 35 MB mailbox limit in place, the outlook mail attachment limit a user experiences is 35 MB regardless of which app shows a larger figure. Microsoft also notes that the full 150 MB is reachable only between users whose messages never leave its datacenters.
For consumer Outlook.com and the old Hotmail addresses, the figure that governs delivery is the one the service advertises to other mail servers, around 35 MB according to our page on the SMTP extension for message size declaration. The hotmail attachment size limit is not published as a separate policy, and the next section is how to check it for yourself rather than trust a number from a blog.
The number that actually rejects your message
Your provider’s limit decides whether the message leaves. The recipient’s limit decides whether it arrives, and the two are set by different organizations who never consulted each other.
SMTP has a mechanism for this. The SIZE extension lets a receiving server advertise the largest message it will take, and lets a sender declare a message size in advance. As our RFC 1870 reference describes it, the server includes SIZE in its greeting response, for example 250-SIZE 52428800 for a 50 MB limit, and the sending client appends SIZE=nnnn to the MAIL FROM command. If the declared size exceeds the advertised limit, the server rejects the transaction immediately, before the payload transfers.
That rejection arrives as a 552 for a permanent refusal or a 452 for a temporary one; both are catalogued in our SMTP reply code reference. A message that dies this way never reaches a spam folder and never reaches an inbox, which is why the sender sees a bounce and the recipient sees nothing at all. The distinction between that and a filtering decision is covered in our note on what separates a block from a bounce.
You can read any domain’s advertised limit directly. Look up the destination’s mail servers first, which our guide to MX records and how to test them walks through, then open an SMTP conversation with the host named there and read the SIZE line in its greeting. The port and transport details for that connection are in our reference on SMTP, IMAP and POP3 ports. The value you get back is authoritative for that domain today, which no published table can claim.
What to do when the file is too big
Ranked by how reliably they work, not by how often they are recommended.
- Send a link instead of a file. Google Drive, OneDrive and every equivalent turn a size problem into a permissions problem, which is the easier of the two to solve. This is the real answer to how to send a file over 25MB on Gmail, and Gmail performs the substitution automatically.
- Shrink the source, not the container. Photographs and PDFs full of images are where the megabytes are. Exporting a PDF at screen resolution, or resizing images before they are placed into a document, routinely cuts a file by three quarters.
- Compress, with a caveat. A ZIP archive helps for text, spreadsheets and uncompressed images. It does almost nothing for JPEG, PNG, MP4 or an already compressed PDF, because those formats are compressed already. It also raises the odds of a filter rejecting the message, since archives are a common malware carrier.
- Split across messages. Workable, awkward, and it fails when the recipient’s gateway counts per conversation rather than per message.
- Ask what the recipient can receive. Two minutes of asking beats an afternoon of resending, and for a repeated transfer to the same organization it is the only approach that does not eventually fail.
One habit is worth more than all of them: attach the file before writing the message. It surfaces the size problem while you still have time to solve it, and it removes the most common failure in business mail, which is the missing attachment rather than the oversized one.
Where the client itself sets the ceiling
The max size for email attachment can also be capped by the program in front of you. Outlook for iOS and Android stops at 33 MB while the same mailbox allows more from a desktop. Older desktop clients carry their own hardcoded ceilings. Web clients apply a browser upload limit that has nothing to do with the mail service behind them.
When one device sends a file and another refuses it with the same account, the client is the variable. Our directory of desktop, web and mobile email clients is the place to identify which one you are actually running, and our page on Gmail SMTP, IMAP and POP3 settings covers the account side of the same connection.
FAQ
What is the attachment size limit in Gmail?
25 MB per message for personal accounts, combined across all files, on sending. For Google Workspace accounts the administrator sets it, and Enterprise Plus was raised to 50 MB for sending and 70 MB for receiving in February 2026. Because the limit applies after encoding, keep the files themselves under about 18 to 20 MB to stay comfortably inside a 25 MB ceiling.
How do I bypass the 25 MB attachment limit in Gmail?
You do not bypass it; you stop attaching. Above the limit Gmail removes the file and inserts a Google Drive link automatically, which is the supported path and the one to use deliberately. The only other genuine reductions are compressing text-based files, exporting images and PDFs at a lower resolution, or splitting the transfer.
How do I send a 200 MB file by email?
Not as an attachment. No major provider accepts a 200 MB message, and even Microsoft’s 150 MB ceiling applies only between mailboxes inside its own datacenters. Upload the file to cloud storage and send the link, or use a transfer service. A 200 MB file would exceed 260 MB once encoded for transport.
What is the maximum email attachment size in Outlook?
The default Microsoft 365 mailbox allows 35 MB for sending and 36 MB for receiving, and an administrator can set anything from 1 MB to 150 MB. The apps cap it further: 150 MB in Outlook for Windows and Mac, 112 MB on the web, 33 MB on iOS and Android. The smaller of the mailbox limit and the client limit is what applies.
Is there a 5 MB attachment limit in Gmail?
No. Gmail has never applied a 5 MB cap. A limit that low comes from something between you and Gmail: a corporate mail gateway, a security appliance, a mailing platform, or an old client with its own hardcoded ceiling. Sending the same file from the Gmail web interface identifies which, since it removes every intermediary except Gmail itself.
Why did my attachment bounce when it was under the limit?
Two likely reasons. Encoding pushed the message past a limit the file was under, since base64 adds roughly a third. Or the receiving server has a smaller limit than yours, and it refused the message with a 552 or 452 reply that quotes its own figure. The bounce message usually contains that number.
Can I increase the attachment size limit?
On a personal Gmail account, no. On Google Workspace and Microsoft 365 an administrator can raise it, up to 150 MB in Exchange Online. Raising your own limit does not help if the recipient’s server is stricter, so for a recurring large transfer it is worth reading the destination’s advertised SIZE value before changing anything.
About the Author
Alaa · LinkedIn
Email infrastructure specialist with 8+ years of hands-on experience in SMTP, deliverability, and email verification. I’ve configured and troubleshot mail systems across Postfix, Exchange, and cloud relays, managed IP reputation and warmup campaigns, and built verification pipelines processing millions of addresses. My work spans DNS authentication (SPF, DKIM, DMARC, BIMI), bounce handling, blocklist monitoring, and compliance frameworks including CAN-SPAM and GDPR. I write every article on SMTPedia to give email professionals, developers, and marketers the accurate, RFC-grounded reference they need.
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