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So I've designed an HTML template to send out some emails on. The code is fine, everything looks great there, and it tests just fantastically. I was sending out putting my recipients in the BCC field, but I decided to make it a little more personal and open the file in Word and do an email merge.

The HTML file itself is 3.06kb and contains an img src to an absolute URL, which is about 125kb (a little large, I know, but it's very important). When I merge the file from Word 2010 -> Outlook 2010, the email size jumps to about 250kb. It's not much, I know, but I'm a gigantic nerd and I'm stuck thinking it should be about 5kb with MIME overhead.

Here's the file list on one of the test emails:

File Size  
image001.png 104366   
image002.gif 43   
Mime.822 152575   
TEXT.htm 5712 

Since the img src is specified, I'm not sure why these are coming through. If this is an issue inherent to Outlook, I'd be happy to explore other options.

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up vote 2 down vote accepted

HTML email is normally self-contained, so Word is probably including the images with each mail, therefore inflating their size, and transforming the HTML as necessary. The images are probably encoded in base64 format, which includes 6 bits per byte, therefore further inflating the email size.

I think (but am not sure) that Word may only do that with relative-addressed images. If the HTTP references to the images are converted to absolute, it may stop including them.

A further remark is that absolute-address images may not display on some mail clients. Even when displayed, if the link to the image contains parameters, these parameters are omitted when retrieving the image as an anti-spam measure.

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Understandable, but isn't it standard to link to images in an HTML email? I can't help but make the assumption that this would work normally in any other mailer (Constant Contact-esque programs) – Nic Feb 28 '11 at 20:00
Well, consider that relative addressing does not exist for the email, since it has no base-document address. Therefore Word just has to convert relative addressing to something that will work, which is including the images inline. It is actually doing you a favor, by automatically correcting the error in your html. – harrymc Feb 28 '11 at 20:24
I think it has that behavior for both absolute and relative. I created the template in NetBeans with absolute addresses in the img tag, then opened it in Word for the merge. I'm pulling my hair out with this, but I understand what you're saying. – Nic Feb 28 '11 at 21:22
If Word is inlining images with absolute address, then this is a bug in Word. You might be able to force Word not to inline by inserting the image as a hyperlink field. If this doesn't work, then Word is simply not suitable for this job. – harrymc Mar 1 '11 at 6:59
@melee: Any news? – harrymc Mar 5 '11 at 8:06

I had the same issue with huge e-mail sizes when doing a mail merge from a Word 2010 document. The file size climbed from 150kb to 4Mb, which is obviously untenable when mail merging with a large number of recipients.

I found a workaround: save the source files as .doc (Word 2003 format) files, not .docx, or .xls (Excel 2003 format) instead of .xlsx. This makes the huge e-mail file size issue go away.

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I have noticed that Word and Excel documents I formerly had in the Office 97-2003 format become huge when saved in Office 2010 format. For example, I have a Word report with a lot of embedded enhanced metafiles that was 1.1 meg when produced in Word 97-2003 that grew to 86.5 meg in Word 2010. I prepared the report in exactly the same way, using the same exhibits and the only change was using Office 2010 instead of Office 97-2003 format. Obviously, this is a problem for storage and email purposes.


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This makes perfect sense. Word 2010 is stored as a .docx format, which is XML (very verbose). Word 97-2003 is stored as a binary format, which clearly would not be as large as a text only XML file. Also, since Word 2010 stores text, any embedded images have to be MIME-encoded to text instead of the smaller binary format (.EMF or .WMF). See for yourself - open a Word 2010 file in Notepad, and then open the same file saved as Word 97-2003 in Notepad. – Ken White Feb 24 '11 at 19:06
Yeah - I understand that there's a new container, but how is that creating issues on a HTML mail merge? – Nic Feb 24 '11 at 22:22

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