IIS Smtp will send plain text but not HTML

[jez]

Hi there,

I am sending email from PHP on Win2003 with IIS 6.
I am using the built in smtp server in IIS.

I can get mail to send, so long as it is plain text.
If i try and send HTML email they just sit in the queue folder.

I turned on logging and found that the messages i get are as follows..

127.0.0.1 HELO - 250
127.0.0.1 MAIL - 250
127.0.0.1 RCPT - 250
127.0.0.1 DATA - 250
127.0.0.1 QUIT - 240

I have looked all over google on this one and the main thing people say is about DNS.
So, i tried the nslookup commands and it does seem to be able to resolve the mx record of the recipient server.

I also took a look at the firewall to ensure port 25 is open.

Lastly i have added the external IP address to the relay and connections in the smtp access settings.


Can anyone give me an idea why IIS SMTP would keep a HTML email in the queue but not an identical one except with plain text.

Thanks.

Jez