Voting Question: Why won't this e-mail go through?

I received an e-mail address from an old friend and it won't go through. I tried sending them an e-mail using hotmail and gmail. Whenever I do a reverse e-mail look up it comes up as being valid and the IP address that they give me matches up with the location of where they currently live, so it definitely seems like it's a real e-mail address. However, every time I try to send them an e-mail, it gets sent right back to me and told me that it was unable to go through. Anybody have any idea why this is? Edit: gmail sends me back a lot of jibberish. Hotmail basically says This is an automatically generated Delivery Status Notification. Delivery to the following recipients failed:

Reverse e-mail look up?

Is there any way I can type in an email address to a website and it give me the name of the user? if so please let me know what the website is. Only if it's free though. I'm having trouble with a fake person on Facebook and I'm really wanting to know who it is. Thank you.

Are there any geuinely free UK people finder.reverse search e-mail, mobile number, services on the internet?

I must have logged on to loads of different companies, organisations and individuals who all say the offer one of the above services free, they never do. Is there anyone genuinely offering free people tracing, reverse number search, reverse e-mail search in the UK. I do realise many of the people are for profit companies and that even for an individual there are costs involved, but if anyone does know of someone or something to help I would really appreciate it and it would save me wasting another two years of my life.