Emails not sending (bounce-back) ?

[Jingo]

Hi one and all-

I've had some difficulty in sending mail to a particular recipient from my hotmail account recently- every time I send the message I recieve firstly a web-master message saying :

Delivery Status Notification (Delay)‏

This is an automatically generated Delivery Status Notification.

THIS IS A WARNING MESSAGE ONLY.

YOU DO NOT NEED TO RESEND YOUR MESSAGE.

Delivery to the following recipients has been delayed:

address @ domain . com

followed the next day by :

Delivery Status Notification (Failure)‏.

This is an automatically generated Delivery Status Notification.

Unable to deliver message to the following recipients, due to being unable to connect successfully to the destination mail server.

address @ domain . com

These mails did contain attachments, ~4 mb. and the second mail ~2mb yet messenger sending allowance is 10mb

If someone could advise resolution on this situation I would be most grateful.

James