Why it’s a bad idea to send large attachments in email

In Tools on November 4, 2009 by TIPS Team

For EPS staff, we all know about the limits in our inbox.  I know I get a message every couple of days telling me that my inbox is full.  Most of the time, this is because someone has sent me a large file attachment – either a co-worker sharing photos of a new baby, or a video that could probably be found on you tube.  So why do people still insist on sharing large files when they know it causes us Outlook grief?  Even with Share (Google) Apps having increased the maximum attachment size to a whopping 25 MB in June, some people want to send larger files. Daniel (another blogger I follow with the  Google Blog) wrote a thoughtful comment that explains why it’s a bad idea to send huge files by email.  Keep these points in mind the next time you have large photos, videos, or files to send:

People who demand large message size limits rarely understand the limitations of the email transmission.

Because of the MIME encoding used when sending binary attachments, your files expand 33% when sent via email. In other words, a 15MB attachment requires 20MB plus the message text, plus message headers.

When you carbon copy 20 of your friends & coworkers, a separate message is sent to each. 20MB x 20 = 400MB. That’s half a freaking CD.

If 5 of those friends are on the same small company email server, downloading those messages saturates the entire bandwidth of their T1 data line for nearly 9 minutes. Because each message has separate headers, it isn’t easily cached and gets completely downloaded by each recipient.
Compare this to uploading the same attachment to a web server, FTP server, file transmission service like YouSendIt, or video streaming site like YouTube. One copy is uploaded. The download is typically 8-bit so minimal expansion factor. The small business’ network can cache the content, so it’s only downloaded once then fetched locally from the web caching server.
Bottom line, sending a large attachment via email is relocating using the U.S. Postal Service as your moving company. It is painful, limited, and expensive.

TIPS on how to share large files: If you’re in Edmonton Public Schools, you currently have access to your own Share (Google) SITES through StaffZone for uploading large files – you just need to make a filing cabinet page for yourself.  For sharing photos, try Picasa or Flickr (you can keep those photos private by adjusting viewing permissions), and Picasa also accepts video uploads even though YouTube is the more mainstream standard.


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