Outlook and Outlook Express
Why when I send an email with an attachments using Outlook do people claim that there is no attachment?

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.