Unable to send mail - 'send' button greyed out

I am using a Dual 1.8 Ghz PowerePC G5 with version 3.6 of Apple Mail. No problems until, suddenly, I am unable to send any emails - the 'send' button is permanently greyed out. Any ideas?

[Spongy]

Hi,

I had this issue on a customers machine a few weeks ago, but can't remember how I fixed it. I think I rebuilt Mail's Envelope Index and for some reason that sorted it. You can do this by closing Mail.app, going into ~/Library/Mail and deleting the Envelope Index file.

If you are running Lion you can't get into the ~/Library folder without unhiding it first, so it may be easier to download a tool like Onyx for Lion and then going to the Automation tab and selecting the rebuild Mail's Index (or similar) and then hitting the execute button and it will be done for you.

HTH

[warragul]

... or maybe you haven't fulfilled one of the conditions necessary for sending mail.
Like an address or subject (trivial examples).