Reducing the size of email attachments

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How can you email a file that’s too big to be sent even after its been compressed.

I think most people know they can squeeze the size of a file using a tool like WinZIP, WinRAR (our personal choice) or many other similar file compressors.

Both those products and many others have options to compress and email directly. Usually you can right-click on a file/s in Windows Explorer, choose the option (the name varies), it’ll make up a compressed file and create an email message with it attached. Add a receiver, subject and message then click Send. Simple, right?

Sadly it’s not always that simple.

Many files are already compressed and putting them into a ZIP or RAR won’t make much difference to the file size. JPG files from digital cameras, MP3 music files and PDF Acrobat documents are common examples of files that don’t benefit much from compression. Microsoft Office documents like DOC usually compress nicely, but the coming Office 2007 versions (DOCX etc) will not benefit from further compression.

Our Office Backup Handbook has a useful list of common file types plus an indication of which are already compressed.

With JPG images you have options to reduce the file size by sacrificing quality and dimensions–

Bur what if a file that is as small as it can get but is still too large for the maximum permitted file size? Then you turn to segmentation – splitting the file into smaller files for sending and then putting them together at the other end.


Thankfully, all the major file compression systems can split a large file into smaller pieces for you. There is no need for special ‘splitting’ software these days.

Check out the help file for your preferred compression program, there will be an option to set a maximum file size (normally it’s unlimited). In olden times this was used to fit large files onto floppy disks (remember them?) and is sometimes used to fit large files onto CD’s – that’s why you’ll often see pre-set options like 1.44MB or 650MB.

You can set any maximum file size you like – for example if the email attachment limit is 10MB then set a file size of, say, 9.8MB.

The program will make a series of files such as ChoreoAnimator.rar ChoreoAnimator.r00 ChoreoAnimator.r01 and so on.

Email each of these files separately with a message explaining what you’ve done (if necessary).

This works even if the original file (JPG, MP3 etc) can’t be effectively compressed, the file can still be split up.

The receiver saves each of the chunks into the same folder then uses their de-compression software to restore the original file. All they have to do is point to the first file (.rar or .zip) and the software will work out that there are associated files that make up the package.

Of course, the receiver needs to have the software to deal with the incoming attachments and the ability to use that software. This is where ZIP’s wide availability is a better choice than RAR which might confuse your correspondents. You also need to have some idea of the computer skills of your correspondent.

Self-extracting archives

In theory, you can send a compressed file that includes the software needed to restore the contents. This is called a self-extracting archive.

A self-extracting archive (aka SFX) is a compressed file (ZIP or RAR) with the extraction program embedded into it. The result is a program file (.exe) that is really a combination of a small de-compression program plus the compressed data. You’ve probably used an SFX file because it’s a common way for small programs and patches to be distributed.

Sadly, these days of virus concerns and blocking of ‘unsafe’ attachments means that emailing a self-extracting archive (which end with .exe ) are often inaccessible to the person you’ve sent it to.

Tip: you can always get past an attachment block by renaming the file. The blocks normally work off the file extension, not the actual contents. Change ChoreoAnimator.exe to ChoreoAnimator.exe.deleteme and it’ll arrive, all the receiver has to do is save the file and remove the obvious extra.

Adobe Acrobat files

Converting documents into PDF files is also an option. PDF will effectively compress Microsoft Office documents into a smaller form that is commonly understood.

Even if someone hasn’t got the Acrobat Reader they can download it for free.

But PDF files are not editable (there are options to comment and make notes) so if you want to send a document and get it back with revisions embedded then PDF is not for you.

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