The main factor for campaigns size is images. The more images you have, the more kilobytes you are adding to your email campaign. The thing to remember with images is that most of the time they are set at a very high image quality or dpi (dots per inch). The default for most images is 200-300 dpi, which is print quality (meaning that the picture can be printed much larger than it is displayed on a monitor). The best to have your images for your email campaign is to have the images at 72-96 dpi, which is email/screen quality. This can mean the difference between having your campaign at over 700kb and getting it down to less than 200kb. Also, look carefully at your email campaign and decide how many of the images are necessary. If you can't reduce your email campaign's size by taking out images, try compressing them.

If you are using MS Word to design and upload your campaign, try the following to lower your campaign's size:

For MS Office 2007:

• Click on any picture you have in your document
• This should bring up the Picture Tools Tab at the top of your document, to the right of the View Tab
• Click under the Picture Tools Tab where it says Format
• On the very left hand side, under Adjust, click on Compress Pictures
• When the Compress Images dialogue box comes up, leave the check box marked "Apply to selected pictures only" blank
• Then click on Options
• Change the Target output to Email (96 dpi)
• Then click on OK, and OK again.

For MS Office 97-2003:

• Click on any picture you have in your document
• You should then see the Picture Toolbar
  • The Picture Toolbar is usually floating, if you can't find it you will need to go into Tools > Customise > Toolbars and find the Picture Toolbar to turn its display on
• Click on Compress Pictures
• This brings up the Compress Pictures dialogue box
• Under Apply to select All pictures in document
• Under Change resolution select Web/screen
• Then click OK

If you are either uploading a zip file, or loading from a URL, try optimising the pictures before completing your webpage and loading them. Optimising an image will usually reduce its size quite substantially without changing its width or height, so if you have already done your HTML and have your layout just so, it's best to optimise/compress the pictures while already in Dreamweaver/FrontPage.

Another factor in the size of the email campaign is the attachments that you add. If your email campaign is 50kb, and you add an attachment of 50kb, the total size of your email campaign when it goes out will be 100kb. For very large attachments (larger than 300kb) we don't recommend sending attachments as the size can get out of hand, rather post the information you would have attached on your website and have a link to it in your campaign. If you must have multiple attachments, rather try compressing/zipping them into a smaller file and attaching that. (See also: how do I add an attachment to my campaign?) Bear in mind that the larger your email campaign is, the more difficult it is for your clients to download.