Email Attachment Size Limits: Fit Your PDF

A PDF that bounces may not have hit the number you looked up. Gmail allows 25 MB(as of November 2026) on personal accounts and Outlook.com allows 25 MB, yet the Outlook app stops messages from either account at 20 MB before the service gets a say.

Exchange business accounts can sit lower still, because they default to 10 MB in the Outlook app. When you cannot see the recipient's setup, the number to plan around is 10 MB.

Four different limits can stop one message

Several limits can apply to one message, and the smallest of them decides the outcome. A provider's published figure is only one of them.

Three sit on your side. The first is the mail service, such as Gmail or Outlook.com. The second is the app you write the message in, such as the Outlook app, which can enforce its own cap before the service is contacted at all.

The third is your administrator, who sets an organization's limit independently of both. A fourth belongs to whoever receives the message; you cannot see it, so it has its own section further down.

• Your service — Gmail or Outlook.com
• Your app — the Outlook app applies its own cap before the service sees the message
• Your administrator — work and school accounts are configured, not fixed

Attachment limits by service, app, and account type (as of November 2026)

Where the limit lives	Published figure	Source
Gmail, personal account	25 MB	Google, Gmail Help
Gmail, work or school account	No fixed figure (set by the administrator)	Google, Gmail Help
Outlook.com, file attachment	25 MB	Microsoft, Sending limits in Outlook.com
Outlook app, internet accounts	20 MB	Microsoft, Reduce attachment size
Outlook app, Exchange accounts	10 MB by default	Microsoft, Reduce attachment size

The lowest figure in the column is 10 MB for Exchange accounts in the Outlook app, and the highest is 25 MB. The next sections take the Gmail, Outlook and Exchange rows one at a time.

Gmail's 25 MB covers personal accounts only

The 25 MB figure is the one for a personal Gmail account. Google gives it in one sentence and then treats work and school accounts as a separate case. If your address ends in a company or school domain, the 25 MB you read about is not your number.

On those accounts the Google Workspace administrator sets the sending limit and the receiving limit, and the two are configured separately. A file you can send is therefore not always a file a colleague can receive. If you cannot ask your administrator, treat 10 MB as the working limit; the section on the recipient's side explains why that is the lowest figure worth planning around.

When a message does go over the limit, Gmail does not refuse it. It removes the attachment and puts a Google Drive link in the email, a fallback covered in the section on links further down.

Outlook.com allows 25 MB, the Outlook app 20

A single Outlook figure cannot be right for both the service and the app. The app checks its own cap first, so even a Gmail address that Google would accept at 25 MB is stopped at 20 MB once it sits inside Outlook.

Outlook.com is a mail service, while the app is a program that opens mail accounts. Microsoft gives the Outlook.com attachment limit as 25 MB. The app, separately, sets 20 MB for internet email accounts, which Microsoft describes as accounts "such as Outlook.com or Gmail", so the same Outlook.com mailbox takes 25 MB in a browser and 20 MB in the app.

Microsoft says the app's cap stops Outlook from repeatedly trying to upload very large attachments that exceed the limits of most internet service providers. The app's cap is a safeguard inside Outlook, not a limit set by the mail service.

Exchange accounts start at 10 MB, the lowest

The lowest default among the limits above belongs to business mail. Microsoft gives 10 MB as the default for Exchange accounts in the Outlook app, and Exchange Online adds a message size limit that covers the whole organization.

That limit is not advisory, and it is not for outbound mail alone. It applies to inbound, outbound, and internal messages alike, so a file sent to a colleague meets the same limit as one sent outside the company. Administrators can raise it, lower it, or set it per user, which is why your figure can differ from a coworker's.

A message over the limit is not delivered, and a non-delivery report (NDR, the bounce message) comes back to the sender. Because Microsoft says the sender receives that report, a send that neither arrives nor bounces is unlikely to have hit this limit.

Encoding inflates the file by about a third

A cap of 20 MB does not mean a 20 MB file passes. Two things make the size a limit checks larger than the file on your disk, and your file manager shows neither.

First, some limits count the whole email. Microsoft states that the Outlook limit includes both the attachment and the email itself, and Exchange Online counts attachments inside its message limit.

Second, mail does not carry raw binary. Attachments are re-encoded as printable text before sending, and RFC 2045, the standard that defines the encoding, puts the growth at about 33 percent. A file just under the cap on disk can be over it in transit.

Where a cap is measured on the encoded message, dividing it by 1.33 gives the size that fits, about three quarters of the cap. That works out to roughly 18.8 MB of file for the 25 MB cap, 15 MB for 20 MB, and 7.5 MB for 10 MB. The message text counts as well, so read those figures as upper bounds and not as targets.

The limit you cannot see is the recipient's

Everything above concerns the sending side. A message can clear all three sending-side limits and still fail on arrival, because the mail app or server at the other end may enforce a smaller cap that you cannot inspect.

Microsoft's Exchange Online documentation notes that an email app can set a lower limit than the service behind it, or cap a single attachment below the message limit. A file that reached one recipient is no guarantee it will reach the next.

Past that size, the service hands over a link

Some documents will not shrink far enough. A long scan stays large because every page is a photograph. For files like that, both Gmail and Apple's Mail Drop offer a link in place of the attachment.

Gmail makes the swap on its own once the total goes over the limit. Mail Drop sends from Mail on a Mac, iPhone, or iPad, or from iCloud.com/mail, and carries attachments up to 5 GB. Each one expires after 30 days, and that expiry makes a Mail Drop link a poor home for a contract or invoice the recipient may need to open months later.

If compression gets such a document under the limit, attach it instead; a link asks the recipient to leave their inbox, and an attachment does not. Compress PDF Online Free: Pick the Right Level covers the compression levels, and Reduce PDF file size without wrecking your scans shows which kinds of PDF shrink and which barely do.

Summary: design for the smallest published limit, 10 MB

The number to design around is not the one your own service publishes. It is the smallest limit that applies to the message. When the recipient's setup is unknown, plan around the lowest published figure, 10 MB.

Three published figures set the range. Exchange accounts default to 10 MB in the Outlook app, the app caps internet accounts at 20 MB, and personal Gmail and Outlook.com both allow 25 MB. Inside the app, the limit counts the whole email, not only the file, and encoding can add about 33 percent to an attachment.

• Unknown recipient or a business mailbox: keep the file under about 7.5 MB, from the 10 MB floor.
• Sending from the Outlook app with a Gmail or Outlook.com account: stay below about 15 MB, from the 20 MB cap.
• Sending from a browser with a personal Gmail or Outlook.com account to a recipient you know accepts that much: stay under about 18.8 MB, from the 25 MB cap.

If one tool leaves a PDF too large, Free PDF Compressor Limits: 5 Tools Compared compares five options by file-size limit, free levels, and whether they upload your file. File size units explained: how many GB in a TB? explains why the same size reads differently in binary and decimal units.