How Do I ... Understand Email Attachments



When sending an email message, you may want to include a document that was created with another application (i.e. a document that is already prepared rather than the message you are typing in the mail package's message window). Examples of documents you may want to send are a Word or WordPerfect file which includes all the formatting information, an Excel spreadsheet, an image, etc.

These types of documents are non-text (i.e. Binary) and cannot be just copied into the message body. They need to be sent as attachments. Most mail packages have a way to send a document as an attachment so that none of the original formatting is lost in the transfer.

The person on the receiving end:

  • must have an email package that can receive the attachment, such as Thunderbird or Outlook.
  • must be able to start the application with which the original document was created, such as Word or WordPerfect, in order to view it properly

File Extensions

It is strongly recommended not to change the default file extension of a document that you are creating with an application such as Word or WordPerfect. The file extension is the three letter code after the "." (e.g. in myfile.doc, doc is the extension). The first part of the file can be anything you like. If the extension of a file that you send as an attachment is kept as the default, then the person who receives the attachment can just double click on the file and the appropriate application will open with that document. If the extension is changed, the receiver may have problems opening the document properly.

Some common default extensions are:

  • doc (Word)
  • wpd (WordPerfect)
  • xls (Excel)

Special Note Regarding Attachment/Msg size

Western allows for a maximum message size of 25 Mb.  However it is important to note that there are a number of other factors that should be considered before sending a message or attachment of this size.  If sending to external mail domains they may have a smaller size restrictions.  You also need to take into consideration the individual quota levels of the intended recipeints.

Transmission protocol (encoding)

In order for an attachment to be sent correctly via e-mail, it needs to be converted into a format that can be sent over the Internet. You need to find out what kind of e-mail package the receiver is using and what kind of transmission protocols it recognizes (e.g. MIME and Binhex are some popular protocols).

The e-mail package takes care of transmitting the document in the proper format automatically and the receiving mail package will automatically convert the document back to its original form.

The most popular type is MIME (Multipurpose Internet Mail Extensions). Most mail packages use this protocol. All of the UWO/ITS recommended mail options support MIME.

Note about viewing attachments that were saved to disk

  • Double clicking on the attachment to open it assumes that you have the appropriate application installed on your PC (e.g. Word if it is a Word attachment).
  • If not, you may be able to read the attachment into another application that recognizes that format (e.g. some times, you can read a Word file into WordPerfect and vice versa).
  • However, there are some exceptions. For example, a lower version of an application generally can't read a document written by a higher version of that application. Also, Word and WordPerfect are not always compatible.
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