It seems as if everyone today is e-mailing photos to family, friends and business associates.

It's certainly fun. And when it's done right, e-mailing photos can be an effective way to communicate.

The problem is, some novice photo e-mailers fail to observe the do's and dont's of sending digital photographic files over the Internet--which, rather than cause someone to smile, may make them frown when they can't open the file or when it takes forever to download the image.

The solution? Follow these basic suggestions:

* Make a copy. To e-mail a picture, you may need to make some changes in the way a picture is stored and sized. The first step in the process, therefore, is to make a copy of your picture and save it under a different name. That way, your original photo remains untouched as you modify your copy.

* File format. Digital images can be saved in several different file formats, each best suited for a specific purpose.

When saving a scanned or digital picture as an attachment to an e-mail, be sure to save your picture as a JPEG (Joint Photographic Experts Group) file. This file format, which compresses an image, speeds up the time it takes to open a file.

Another time-saver is sending a JPEG image at a low or medium setting; high and maximum settings take more time to send.

* Picture and pixel size. Large pictures take longer to transmit and download than small pictures. So do pictures with lots of pixels per inch (ppi).

If you want a picture to open up rather quickly on a computer monitor, do two things: choose a relatively small picture size (5 by 7 inches), and select a ppi of 72. If the picture is going to be used only as a screen image, there is no advantage in using a higher ppi, because that's the resolution of a computer monitor.

If you intend your picture to be printed at the other end, then you would want to save it at a higher ppi.

The only time you would want to use a higher ppi (say 300 ppi) and a high or maximum JPEG setting is when the person receiving your digital picture wants to make a high-quality print, or perhaps use it in a newspaper, newsletter or magazine.

* Ask before you click "Send Now." Trying to open up a photo file can drive someone who is not familiar with receiving e-mail photos nuts.

To avoid this frustration, ask your e-mail pal if it's okay to send a photo file as an attachment to a document. If you do, he may offer some advice of his own on how to send the file in a way that is best for both of you.

* PC or Mac? The same picture will look slightly brighter on a Macintosh monitor than it does on a PC monitor, even if the two monitors are calibrated correctly. With this in mind, it's helpful to know what system your recipient is using, especially if you are a stickler about how your pictures look. Also, a picture looks slightly lighter on a monitor that is just turned on than it does on a monitor that is "warmed up."

* Forwarding pictures. When you send a photograph as an attachment to an e-mail, keep in mind that the recipient can, in turn, forward it to anyone on his address list or even make a print.