I am trying to send an email to my friends via the email client, but every time I select their emails from the contacts the email client doesn't put the emails addresses into the "To : " field, the only way to send an email is to write the email address manually which is not practical at all, is it a bug or am I doing it wrong ?

hotmail status notification says I am trying to send an email to
myfriendfirstname@BLU0-SMTP2109.phx.gbl

After selecting a contact or contacts, are you pressing the 'Done' button? If you leave the contect dialog without pressing this button it will ignore your contact selection(s).

if I choose someone's email from the contacts only his first name shows in the "To:" field
like this:
"Firstname;"

without the email address

I think I've figure it out, it because there is a non alphabetic character in the first name field

since the n900 doesn't have categories for the contacts I used tags like "<Family>" and "<Friends>" instead in the first name field... looks like it didn't work out.

should I report this as a bug ?

Yeah, don't use '<' or '>' in email names. And no, I wouldn't report this as a bug.