An attachment is a computer file or files placed inside an email message.
To attach a document to an email message drag the file attachment to the body of the message and drop it. An attachment can also be added by choosing File Attachment from the menu. Most modern email programs place a button on the Toolbar that can be clicked. A dialog box will open that allows you to browse and select the file that you want to attach. More than one file can be attached to a single email message. Once it is attached, don't move or delete the original document until the message has been sent.
Most documents created on computers, such as word processing documents, spreadsheet documents, or graphic files are stored in their own unique binary code format. This binary format is determined by the program that the file is created with. Email documents are created as text files so in order to send a binary file or document via email, it must first be encoded into a text format and then attached to the email text message.
Such an 'encoded' document may end up looking something like this:
ugAAANAAAAALAAAAAgD//zQAQgBvAGQAeQAgAFQAZQB4AHQAAABCAG8 AZAB5ACAAVABlAHgAdAAAANMFCwAAAQAACwDT0wQdAAATAAD//wUAsA QAmA0AEA4AaBAAK5sdANPUGxkAgAEAAAgAigIAAAAAAACKAooCGQDU1 BpXAIABAQAIAAAAAAAAAAAAHAD0GlwSGgkAABEJAAAAYAAYEQAAECoA VABpAG0AZQBzACAATgBlAHcAIABSAG8AbQBhAG4AAAAAAAAAVABUAAA AVwDU1AILAAABAAELANTUAwsAAAEA
These lines are all printable ASCII characters and can be sent via email. When it gets to your computer and you want to view the document, it first must be decoded or converted back to it's binary format before it can be opened. Today this is typically handled automatically by your Email program.
There are several common encoding standards, the most popular being uuencoding, mime, and binhex. Not all email packages support even these three, let alone all the non-standard ones. If someone sends you a document encoded in a format that your email program doesn't support the email program will not decode the attachment.
The attached file must be loaded into a program to be viewed. For example, if the attached document was originally created in Microsoft-Word you need Word compatible word processor on your computer to work with the document. Most modern software suites can import documents from other suites.
Most modern email programs work hand-in-hand with your operating system to try and open the correct program required to view the document sent as an attachment. This is done by matching the file extension such as .jpg, .gif, .doc, etc... with a registered file type.
Viruses can also be transferred via email attachments. Because your email software handles the decoding of programs sent as attachments it is easy to infect your computer simply by opening an infected attachment. Always check email attachment with an anti-virus program before opening them and never open an attachment from an unknown source..
There are several reasons why an attachment will not display properly or at all:
- the encoded file is corrupted and cannot be decoded. This is usually due to damage in transit and happens very seldom these days
- the encoding type is not supported by your e-mail program and so the file cannot be decoded back to it's original type
- the attached document was created in a program that you don't have on your computer or is not a registered file type
- the email program has a security option set which automatically locks attached files
When sending an attachment you should think about whether the intended recipient has the same program on their computer. When you are sending an attachment to someone you should always use a standard encoding process (the one that comes with your email program is usually best) and send the document in a format that the recipient can view. If in doubt, ask them first by email.
Attachments can also be used to send private and confidential documents by encrypting files. An encrypted file will require a password or an decryption key to unlock it before it can be viewed.
If your email software automatically locks attachments and you want to view the attachment you can change the program's settings by modifying the Preferences or Options.
Last update: March 5, 2017