Attachments are one of the most common sources of email frustration. Here’s what’s actually going on with size limits and file-type restrictions.
Why size limits exist
Most providers cap attachments between 20 and 25 MB. This isn’t arbitrary — email infrastructure was built for small text messages, and large files strain mail servers and slow delivery for everyone. The limit has stuck around even as internet connections have gotten much faster.
Why some file types get blocked
Executable files (.exe), scripts, and certain compressed archive formats are frequently blocked automatically because they’re common vectors for malware. If a legitimate attachment gets blocked for this reason, renaming the file extension or compressing it differently sometimes resolves it, but always confirm the file is genuinely safe first.
Common workarounds
- For large files: use a cloud storage link instead of a direct attachment (see our guide to sending large videos for a video-specific version)
- For blocked file types: compress the file into a standard .zip archive, which is rarely blocked
- For multiple small files: combine them into a single .zip to reduce clutter and attachment count
A few best practices
Compress large files before attaching when possible, use descriptive file names so recipients know what they’re opening, and avoid attaching sensitive documents without password protection when the content is genuinely confidential.
Frequently asked questions
What’s the most common attachment size limit?
Around 20-25 MB is typical across most major providers, though it can vary slightly.
Why was my .zip file blocked?
Some providers scan inside zip files for blocked content, so a zip containing a blocked file type may still get flagged even though .zip itself is generally allowed.
Is it safe to open any attachment from someone I know?
Not automatically. Compromised accounts are sometimes used to send malicious attachments, so unexpected files from familiar senders still deserve a moment of caution.