Problem with Hotmail

[#1]

I use Hotmail. When I send a message to a friend who has an AOL address it comes back as unable to connect to server. It originally only did this when I used the reply button but now does it even with a new message, He has not blocked  me. I have no problems sending emails to others although nobody else I communicate with is on AOL. When I use my gmail to send a message to him it gets through so I can get round the problem but just wondered if anyone could tell me what is happening.

[#2]

Whilst your friend has not blocked you, it could be that AOL's servers have blacklisted hotmail servers (for spam, for example) this is quite common, because Hotmail anyone can sign up for an account and then use it to spam.
In a few days/weeks it may start to work, before being blocked again.
Best thing to do is move away from "free" services if you can, altho services like gmail (who take a no-nonesence, do it and get out attitude to spammers, are better to use) are normally pretty reliable.
That would be my best guess at a "cannot connect to server" response. (That, or AOL is having issues, changed a DNS record or something along the lines, and Hotmail hasnt updated -- but this ones *really* unlikely)
Regards