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Reducing Email Attachment Sizes With Compression

By April 22, 2011April 16th, 2014Tutorials

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In this video, I’ll be demonstrating how to use compression to overcome attachment size limits in emails. As an example, I’ll be using Gmail, which has a maximum attachment size of 25 megabytes. I’ve prepared two scenarios where the size of the attachments exceed the limits enforced by Gmail. In the first scenario, I’m looking to send pictures through email; however, I have exactly 25.1 megabytes of pictures, which is slightly over the Gmail limit. To get around this, I’m going to combine all the pictures into a special compressed file, which will be smaller in size. File compression is included in Windows and requires no additional software to compress files in windows.

  • First select all the files you wish to compress.
  • Right click one of the selected files.
  • Select send to,¬†and then select compressed zipped folder.

Now that the compression process is completed, a file with the extension .zip has appeared in the folder. This file should now have a smaller size than the combined total of the pictures. Sure enough, when I view it in Windows, it has a total size of 24.9 megabytes whereas we previously had 25.1 megabytes for all the photos together. It’s important to remember that this file now contains all of the photos we selected earlier, and if I launch it here, you’ll see what I mean. They’re all listed. Keep in mind that what I’m seeing here is actually enhanced by third-party software, but in Windows, opening a compressed folder (compressed file) is the same is opening a folder, so you will see the contents with all the photos much like what I am seeing right here.

At this point you may be wondering about the efficiency of the approach given that we saved only 0.2 megabytes. The pictures I chose to compress were all in the JPG file format and JPGs, by nature, are compressed images. In fact, many multimedia file types are already compressed significantly by the time they are produced. On the other hand, text files and executables are usually not, so they tend to compress better. At the very least, compression reduces the number files of that need to be uploaded to an email client, simplifying the act of moving them around. In this case, the recipient would receive only one file, and after it is uncompressed on his side, all the photos will be available… and it only took one email.

In the second scenario, I have significantly more pictures to send. Given that their total size is equal to 44.1 megabytes, I will have to change my approach. Rather than compress all photos into one compressed file, I will create multiple compressed files and send multiple emails. While I could simply select a subset of the pictures and create two compressed files via the Send To menu, I will instead use a compression program called WinRAR. WinRAR can be acquired from, and is free to evaluate.

WinRAR introduces a new compressed file format, represented with the extension RAR. It is similar to the ZIP file, but requires WinRAR to be installed. It has a nice feature that allows RAR files to be automatically split into parts, which will be useful in my case. To create a multipart RAR file:

  • Simply select all the files you wish to compress.
  • Right-click any one of them
  • and select add to archive

This option will appear after WinRAR has been installed. Once WinRAR appears, it will ask you for an archive name, the archive format, compression method and other options. The one we care about at the moment is “split the volumes”. What this will allow us to do is instruct WinRAR to limit the size of each part in the multipart set. So since WinRAR requires bytes in this case “split to volumes bytes”, we will need to use a free online converter which will accept the friendlier megabyte format and change that into bytes. So I have a site right here which I will put in the description which will allow me to do just that. So when I enter 25 megabytes into this site and click on this button below, it automatically provides me with the bytes, kilobytes, gigabytes, terabytes. Right now, we only want bytes, so I will copy this and return to WinRAR. I will provide it with the bytes in the field right here, and click OK.

Now WinRAR will start doing its work – we simply have to wait and once it’s complete we will have two RAR files. You can see right here that it is already talking about part two – we already have two RAR files. Now that it’s complete, I will show you the RAR files right here: scenario two, part one and part two. Now what we can do is simply attach each of these RARs individually to their own emails. So I have an email open right here in Gmail – I will drag the first RAR file into it, and I can send it and simply create a new email and send part two. Once the person receives these RAR files, it’s really as simple as clicking on any one of them, and dragging the contents elsewhere. WinRAR figures out putting them together, and you don’t have to worry about that – so, multiple files, but they’re treated as one when they’re finally collected at the end.

So those were two scenarios that illustrated how compression could be used to get around attachment size limits. If you have any questions about what I presented, please feel free to leave me a comment. I’d be happy to answer them, thanks.


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