I receive a few e-mail newsletters from various organizations, as part of my executive role in the Editors' Association of Canada. Two recent issues of one of those newsletters were accompanied by extremely large file attachments—this month, two Microsoft Word documents and a TIFF image that was, by itself, 2 MB in size.
I'm not sure how many people receive the newsletter in question, but even if that number is fairly small, sending such large files—or attachments of these types at all—is generally not a good idea.
I've been working with Internet e-mail since 1990, and in that time I've found that oversize attachments and improper file types cause some of the biggest problems for both senders and recipients. Here's what I wrote to the sender of this particular newsletter (after a polite introduction, of course):
- Many anti-spam filters consider e-mail with attachments that the recipients are not expecting to be a sign of spam e-mail, and may tag or route the mail so that the recipient never even sees it.
- Microsoft Word documents can contain macro viruses, which can cause problems with recipients' computers, especially if they use Windows. Even if your files are clean, some recipients (or their anti-virus software) may reject the mail because it includes Word files. If it is necessary to send formatted documents, Acrobat PDF files are much preferable, because they are not editable, are not subject to viruses, do not require anyone to own Word (the Acrobat Reader is free), and are usually smaller. If you must send files that can be edited by the recipients, rich text format (RTF) is better because more programs than Word can read it. If it is possible to include the appropriate text in the body of the e-mail message itself, great.
- Some recipients may not have software that can easily read TIFF images such as the one you sent. JPEG images (.jpg or .jpeg) saved at high quality offer nearly the same reproduction, but at both much smaller file sizes and with greater compatibility to a variety of computers. Most people can even see them directly in their e-mail programs, which is not necessarily true of TIFFs.
- Any attachments over about 200 KB in size (i.e. as little as 10% of the size of the ones you sent) can cause problems in various ways. Many people's e-mail accounts won't accept attachments much larger than a few hundred KB, or may have low mailbox quotas, so your single message may fill up their mailboxes so that further e-mails from other senders will be bounced until they clear it out. Also, anyone using a dial-up connection might have to wait as long as 15 minutes (!) for your single e-mail to download to their computers before they can read anything that came after it, which could be annoying, to say the least.
- Sending out many e-mails with large attachments can actually cost you significant money—Internet bandwidth does incur costs, and large attachments can eat up bandwidth rather quickly when sent over and over. People receiving the messages usually have to pay too, though often they are below their bandwidth limit and never trigger additional charges.
- In general, then, it is best to convert files you are sending via e-mail so that their combined size is less than 200 KB, and so that they are in more standardized formats. Even better would be to post the relevant files to a website (with a password if necessary), and then include links in the e-mail that people can click to view them if they wish. Then only those who wish to see the material actually download it, and they can be prepared to wait if the files must be large, such as if they are video, audio, or very high-quality images.
If you want to read up about attachments, try Adam Engst's article from four years back, "E-mail Attachment Formats Explained."