Email providers cap attachment sizes — commonly around 20–25MB, but corporate systems are often stricter. If your PDF won't send, here's how to shrink it.
Compress first
For image-heavy PDFs, compression alone usually gets you well under any email limit. Start with a moderate setting and check the size.
Split or link if still too big
If a document is genuinely huge, split it into parts, or share a link instead of attaching the file.
Step by step
- Check the recipient's limit, not just yours — many corporate systems cap at 10 MB.
- Compress to comfortably under that figure; attachments grow slightly in transit.
- If it still will not fit, split the document or share a link instead.
- Send a test to yourself first for anything important.
What usually goes wrong
Encoding inflates attachments by about a third
A 9 MB file can arrive as roughly 12 MB of message. A file just under the limit may still bounce.
The strictest limit wins
Your provider might allow 25 MB and theirs 10 MB. The smaller number is the one that matters.
Bounces are often silent
Some systems drop oversized mail without telling either party. If a large attachment goes unacknowledged, assume it did not arrive.
Frequently asked questions
What's the typical email attachment limit?
Often 20–25MB for consumer email, but many workplaces enforce smaller limits. Aim well under to be safe.
What size should an email attachment be?
Under 10 MB is safe almost everywhere. Above that you are relying on both providers being generous.
Why did my 20 MB attachment fail when the limit was 25 MB?
Attachments are encoded for transport, which adds roughly a third. Compress to well under the stated limit.