Outlook POP and IMAP Attachment Limit: 20 MB
Direct answer
Outlook desktop's own 20 MB check for POP and IMAP accounts, and the PDF size that fits it.
Why this matters: BytesPDF processes the file on your device and does not send it to a compression server. Delivery by email or portal is a separate step.
For POP and IMAP accounts, Outlook desktop applies its own 20 MB check before anything is sent. This is separate from the mail server's limit. Plan around the safe size below, and check the message if Outlook reports that the attachments exceed the limit.
PDF Compression Core
Recompress supported PDF images locally with an adjustable quality and size trade-off.
or drag and drop PDFs here
PDF files only · Max 150MB per file · Up to 10 at a time
Limits
Outlook POP and IMAP Limits
Use these checkpoints with the destination's current instructions. Requirements can vary by account, institution, region, document type, and workflow. BytesPDF does not verify or guarantee recipient acceptance. Page reviewed . See the browser-local processing architecture.
| Portal / Recipient | Requirement / check |
|---|---|
| Client check (POP or IMAP) | 20 MB total attachments per message |
| Safe PDF size on disk | About 14 MB |
| Raising the client check | Registry value; the mail server limit still applies |
| Larger files | Send as a OneDrive or other cloud link |
Trade-offs
Which Compression Mode Should You Pick?
Three modes — pick based on what the recipient needs to do with the file.
✅ Text documents
Usually the best candidates. Check the result before sending.
🟡 Scans and photographs
Expect softer detail. Compare with the original.
🟡 Digitally signed or fillable forms
A digitally signed file is not compressed, because compressing it would break the signature. Check form fields in the output before sending.
Before compressing a high-stakes document
Compression rewrites the PDF. BytesPDF rejects files containing a cryptographic signature because any rewrite would invalidate it. Keep digitally signed files and required PDF/A archival masters unchanged. Bookmarks, links, forms, annotations, accessibility tags, and color profiles are preserved where the PDF library can retain them, but always inspect the downloaded copy before filing or submitting it.
What is the attachment size limit in Outlook desktop for POP or IMAP?
Can I raise the 20 MB limit in Outlook?
Why does Outlook say the attachments exceed the limit?
Ready to get under the limit?
Drop your file in — the compressor runs in this tab, so nothing is uploaded. Outlook desktop's own 20 MB check for POP and IMAP accounts, and the PDF size that fits it.
No account · No signup · No watermark · No PDF upload
Editorial review: Limits come from the BytesPDF guides linked on this page and were checked on October 15, 2026. Mail and portal rules change, so confirm the current limit on your account.
Last reviewed: . We update this page when provider guidance or tool behavior changes.
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Limits and examples are informational and may vary. Confirm the recipient's current requirements before submitting a high-stakes document. Digitally signed or archival-conformance files should be submitted in their original form.