Email Attachments: Best Practices

Students, staff and faculty now communicate very well by email. There are simple things you can do to use email even more effectively to get your message across1.

Sending Email Attachments

  1. Send the message in the body, not in an attachment.

    Avoid using attachments if you can send the message in the body instead. Some email reading tools do not handle attachments well. Using attachments makes the recipient take extra steps to read your message. Attachments are the primary way viruses are transmitted. Attachments are often in a proprietary format (such as Word, Word Perfect, Excel, and so on) that the recipient might not have the software to read. That software can be expensive, and might not work on every operating system. Reading attachments in proprietary formats is especially hard for recipients who use Unix or GNU/Linux or who lack the funds to upgrade proprietary software annually.

  2. Use non-proprietary formats.

    If you want more formatting than a simple email message can provide, consider using a non-proprietary format such as HTML (.htm, .html), Rich Text Format (.rtf), or Portable Document Format (.pdf) in preference to proprietary formats such as Word (.doc). More people will be able to read your message; there is a smaller chance you will inadvertently transmit a virus; there is a smaller chance you will compromise your own privacy accidentally; and you will save University resources--the files are much smaller. You can use your usual word processor to write documents but still save them in a more accessible, compact and safer format to send them by email. Help is available to learn how to save documents in these formats. The pros and cons of several common document formats are tabulated below. Security risks, privacy compromises, and hidden costs inherent in email attachments are detailed in the appendix.

  3. Attachments are a way to send files, not messages.

    However, if you really need to send a file (such as a spreadsheet) to a particular individual so that person can work with it, attaching the file to an email message can be an effective way to transmit it--if the file is not too large. If you just want the recipient to be able to read or print the information, send the information in the body of the message or use a non-proprietary format: there is a better chance the recipient will be able to read your message.

    Email attachments should be used to send only moderately-sized files (less than 0.5MB or so) to a small number of recipients (up to 10 people). Larger files or larger recipient lists can cripple email servers. If a large number of people need to work with a large file, consider posting the file to a web site and sending just the URL by email, or transferring the file using FTP or SFTP.

Thank you for taking the time to read this.

Remember: Think Before you Click!

Email Attachment File Types: Pros and Cons
Format Editable? Cross Platform? Secure? Compact Proprietary Advanced Formatting? Permanent Cost
Plain Text ASCII (TXT) Yes Yes Yes Yes No No Yes Free
HyperText Mark-up Language (HTML,HTM) Yes Yes Variably [1] Yes No Yes No Free
Portable Document Format (PDF) No Yes Mostly [2] Yes Yes Yes Largely [3] Free
Rich Text Format (RTF) Yes Partly Yes Yes Yes Some [4] Yes >$5
Word Document (DOC) Yes No No No Yes Yes No >$20


[1] Often HTML that is authored within an email program (such as Eudora or MS Outlook) is secure. However, HTML email that you receive can have web bugs or other security vulnerabilities. It is important to understand what the default security settings of your email program are and that the default settings can be insecure. Some things you might want to do are 1) turn off cookies within emails, 2) not allow scripts to run in emails and 3) open your email off-line to avoid web bug tracking.

[2] PDF is largely a secure format. It does allow some basic scripting and URL linking which can be used to run programs on your system and to track where the document is being viewed on the Internet.

[3] PDF undergoes changes regularly although it is expected to remain backward-compatible.

[4] Some advanced formating is available in RTF.

APPENDIX: Details of Security Risks, Privacy Compromises, and Hidden Costs

Attaching documents to email is often unnecessary, costly, exclusionary and risky, and transforms UC Berkeley in a way that burdens some units financially. This can be illustrated by looking at one of the most common email attachment formats: Microsoft Word. (For example, minutes and agenda of administrative and Academic Senate committee meetings are often sent as Word email attachments.) Some of the following discussion is specific to Word Documents but most of the comments apply to email attachments in general.


Exclusionary Impact

Security and Privacy

Word has features to track changes in documents by several co-authors. When a group of authors collaborates on a document they have agreed to write in Word, it can be appropriate to send the manuscript back and forth by e-mail. However, Word documents are used principally for the formatting capabilities of Word, not for more advanced features. Unless the advanced features are really needed, there are advantageous alternatives to Word, depending on the amount of formatting the user desires: plain text (TXT), hypertext (HTML), Adobe's Portable Document Format (PDF) and rich text (RTF). The features and limitations of these formats are delineated in the table in the body of this document.

The alternative formats are much safer for the sender and the recipient. (However, note that when a Word document is saved as html, which preserves much of the formatting and makes the document more accessible, Word embeds potentially sensitive information in the html document.)

In conclusion, please be sensitive to accessibility, security, and cost when you send email. Send plain text in the body of the message when that will get your message across. If you need more advanced formatting to achieve your goals, use the safest and most accessible format you can. Send (or post) final versions of formatted documents in HTML or PDF.


Help is available... Saving in different formats:

FTP stands for "File Transfer Protocol." FTP is the standard way to transfer files over the Internet. SFTP is a secure version of FTP that encrypts all information, including passwords. Mac OS X and most Linux distributions include both ftp and sftp (type 'which ftp' or 'which sftp' at a terminal command-line prompt to see if your system has it installed.) Most Windows systems and older versions of Mac OS include FTP but not SFTP. The programs SSH and MacSSH--available from SFTP for Windows and Mac OS, respectively.

About this document: This document was written in LATEX and translated to PDF using dvipdfm and the hyperref package. The HTML was created using LATEX 2HTML5. Last modified 4 May 2003 by Joseph Lorenzo Hall (


... across1
©2003 University of California at Berkeley--Educational Technology Committee. Previous drafts of this document are available here: 2nd draft, 1st draft. This document is located here: PDF.
... products2
By limiting the utility of other software products--such as the free operating system BSD, developed here at UC Berkeley--we are limiting our options and increasing costs. see:
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See Symantec's Gallery of the Word Macro Virus Family:
See The Privacy Foundation's FAQ on Document Web Bugs:
The following command was issued to LATEX2HTML:
latex2html -split 0 -nonavigation -noinfo -noaddress attachments.tex