Outlook Email Expansion

Many believe that e-mail will often expand to double the size of the original PST or MSG.  That may very well be true, but have you ever wondered why?

Many processing tools allow the technician to choose what format should be used for e-mail messages.  These choices normally include MSG, HTM, and MHT.  Other tools do not give the technician the option and simply import the e-mail messages as MSGs.  This is where the expansion happens.  When importing MSGs, the software is essentially importing the original message (attachments still intact) and extracting that message’s attachments as separate documents.  This import would absolutely almost double the size of the data imported.

Here’s why…

RE: January Invoices.msg (e-mail message at an assumed .5 MB plus three attachments) ->  10 MB

This e-mail gets imported into the processing tool and is “expanded” as follows:

  • RE:  January Invoices.msg -> Still 10 MB
  • Attachment 1:  NewClientPresent.ppt -> 3.5 MB
  • Attachment 2:  PricingInfo.xls -> 1.5 MB
  • Attachment 3:  MarketingMaterials.pdf -> 4.5 MB

Total amount of data imported = 19.5 MB

With one e-mail message and attachments, this isn’t really a big deal.  But, what about those instances where you have collected hundreds of thousands of e-mail messages?  The numbers can add up quickly!

The solution is to import the original e-mail and choose, if possible, to import it as an HTM or MHT file and you get a significant reduction in size.  The reason for this reduction is that an HTM (or HTML) file is a text file and an MHT (or MHTML) file is a cousin to the HTM/HTML file, but it keeps links intact as well as embedded images/objects (like those pesky company logos in signature blocks).  A text file takes up much less space than does an MSG with attachments.

Here’s the same example, showing MHT instead of MSG:

RE: January Invoices.msg (email message plus three attachments) ->  10 MB

This e-mail gets imported into processing tool x and is “expanded” as follows:

  • RE:  January Invoices.msg -> Now .25 MB
  • Attachment 1:  NewClientPresent.ppt -> 3.5 MB
  • Attachment 2:  PricingInfo.xls -> 1.5 MB
  • Attachment 3:  MarketingMaterials.pdf -> 4.5 MB

Total amount of data imported = 9.75 MB

This small change in processing specifications could mean a huge difference in hosting charges!  This also means a big drop in the amount of space being used on your servers.

Having said that; ZIPs, RARs, JARs, 7Zs, etc. will almost certainly inflate the size of your data set when they are extracted.  However, the size of the files extracted from these types of archives should be easy to calculate and, depending on the frequency of these types of files within your data set, will not normally double the size of the original data that you handed over for processing or hosting.

So, if you have noticed a consistent doubling of the size of your e-mail when processed, you might want to check with the team processing your e-mail collections and find out if they have the option to convert those e-mail messages to HTM or MHT.  It couldn’t hurt and could save space and hosting charges.

Do you prefer to host MSGs anyway?  I would love to hear your perspective!

~CAtkins

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About CAtkins Support

All opinions posted here are mine and do not necessarily reflect those of my employer.
This entry was posted in eDiscovery, Litigation Support, Technology and tagged , , . Bookmark the permalink.

2 Responses to Outlook Email Expansion

  1. I am not sure where you’re getting your info, but good topic.

    I needs to spend some time learning more or understanding more.
    Thanks for great info I was looking for this information for my mission.

    • Thanks for taking a look!

      The information is coming directly from my personal experience with Outlook e-mail messages and ESI processing software.

      Best wishes with your studies!

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