Last month the LStech list had a significant discussion about protocols around the size of email attachments.  Someone suggested that NTAP do a little research around email attachment protocols and report back. Here's what I found.

What are LStech readers doing about attachment size limits?

First of all, the general consensus among respondents to the thread on LStech was to limit email attachment size to 10 - 20 MB and to strictly limit the transfer of executables by email as an antivirus measure.  Several respondents suggested using file sending and sharing alternatives - specifically Pando, Box, and SendthisFile.

(If you're in a hurry, just scroll to the bottom of the page, because web-based file sharing services are still probably the best workaround for this problem and TechCrunch recently posted an article comparing 16 different sharing apps.)

Why limit message size at all?

Limiting message size improves security and network management:

A 2006 blog entry from Microsoft's Exchange Server team suggests that failing to establish attachment size limits 

• makes a network vulnerable to denial of service attacks (because attackers can dominate more resources by sending mail with larger attachments)
• makes it more difficult to plan future capacity for a network
• creates a larger database size that impedes backups and interferes with virus scanning and anti-spam measures
• may create a strain on the network because of the sheer size of files being transferred.
  

It's an industry standard: 

Even if you change your settings, your mail may be returned by the server receiving it because the industry generally sets size limits on incoming email messages.  Here are some of the standard defaults:

So setting larger attachment size limits could be counter productive. The fact remains, however, that members of the legal aid community (and indeed, the rest of email users) are being asked to collaborate on and transmit larger files than they used to be.  (One LStech reader noted that submitting 60-80 page electronic filings is becoming routine.)

What are the possible solutions?

Unless industry standards shift across the board, all of these solutions mean asking users to step outside email to make their oversized files available.

For ongoing projects, users can share files via online project management tools (this has the added bonus of helping team members track the most recent versions of files), but various project management tools also apply certain file size limits for upload:

If users need to share a file for external consumption, they can

• Share files via a website or offer a link to content on a server – pdf is often a useful format here.

• Send files via a link in email.  There are a variety of web applications that transfer larger files and I was going to collect all that information and list it for you.  Luckily Technola recently shared 16 Apps That Make Sharing Large Files A Snap (TechCrunch, August 8, 2009).  That article offers a nice feature comparison table and brief reviews of 16 file sharing apps, but there is also a lively discussion of other options in the comments.
  

Further Reading:

• 16 Apps That Make Sharing Large Files A Snap (TechCrunch, August 8, 2009)
• The Email Attachment Problem and How We’re Not Solving It (Web Worker Daily, May 5, 2008)
• Thinking about Mailbox and Message Size Limits  (The Microsoft Exchange team blog, July 6, 2006)
• Email Attachment Policies (Reach the Public, May 13, 2008)
• How to Send Really Big Email Attachments (Digital Inspiration, September 1, 2006)
• Avoiding the Dreaded Email Attachment (Idealware, July 7, 2009)
• Wikipedia on Email Attachments

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