Why when I try to open an attachment is it greyed out and I can't open it?

A common problem when using Microsoft Outlook Express Version 6 is to try and open an attachment in an email, but find that it is greyed out and you can't open the attachment.

This is caused by Microsoft making the default selection within the virus protection section of Outlook Express version 6:

"Do not allow attachments to be saved or opened that could potentially be a virus."

In fact, all Outlook Express does is prevent access to certain types of file which can contain viruses. It does not actually look inside the file and attempt to determine whether there really is a virus. So if you are expecting the attachment and simply want to open it, you can change this behaviour and open the attachment normally.

In order to change this setting you must run Outlook Express Version 6, then select Tools -> Options then select the Security tab, you will find that "Do not allow attachments to be saved or opened that could potentially be a virus." is ticked. Untick it, and click OK.

You should now be able to open attachments that you receive via email.

Be careful! These attachments could potentially contain a virus, be very cautious of .exe and .scr filetypes. The best protection will be to install a virus check, for more information on virus checkers click here.

A common problem when using Microsoft Outlook is to send an email with an attachment to someone using Microsoft Outlook Express and find that they claim there is no attachment. If you look at the size of the received email you will usually see it is rather large for just a text email - the attachment is actually there, you just can't see it!

This is caused by the WINMAIL.DAT file format it uses.

If you have Outlook set to send messages using RTF format, then any attachments you send will be combined into a file called WINMAIL.DAT which is attached to the email. RTF is, in theory, a "standard" format, but each application which uses it seems to use a different version of this standard. In fact, the only software which understands these WINMAIL.DAT files is Microsoft Outlook.

Attachments sent in WINMAIL.DAT format will be unusable to those who do not use Outlook - even Outlook Express (as supplied free with Internet Explorer) does not understand these files. Even worse, the way that the attachment is added to the email means that many email packages will not even show that there is an attachment present. If you have ever been told by someone that an attachment was missing from an email you sent, then this may be why!

It is our strong recommendation that you disable the use of RTF within Outlook. To do this, in Outlook select Tools -> Options -> Mail Format. If the current selection under Message Format is "Microsoft Outlook Rich Text" then change it; we would suggest either "Plain Text" or "HTML". Different versions of Outlook (and different configurations) have different options and in different places - if you are stuck let us know.

Update: A range of tools are now available to extract information from WINMAIL.DAT. You first need to extract WINMAIL.DAT from the email, which isn't straightforward with Outlook Express because it pretends it isn't there. However, if you save the email (File -> Save As or just drag it from the message list onto your desktop), and then open it with WinZip, you should be able to extract the WINMAIL.DAT from there.

You can then open WINMAIL.DAT with Fentun (available for Windows and Linux), or TNEF or YTNEF (better tools, in our opinion, but not available for Windows).

Alternatively, if the WINMAIL.DAT file is small, you can use TNEF online here.

These workarounds can be useful when you receive emails in this format, but should not be used as an argument in favour of sending in this way! If you use Outlook we still recommend that you change the settings as above to avoid the problem, rather than refering people you correspond with to this page.