I had a similar issue around the office on Outlook 2007 and I found a simple work around for this. Just change the format of your message to rich text by selecting “Options”, “Format” , “Rich Text”. You
can send the message without any problem.
If your problem persists try turning off Word as your email editor like this:
1. From the main Microsoft Outlook window, click the Tools menu, click Options, and then click the Mail Format tab.
2. Select or clear the Use Microsoft Word to edit e-mail messages check box.