well, i had this situation :

a user used the contact form to ask me about some products information (@eb3t)
i clicked reply, wrote the perfect answer..
then SEND..
few seconds.. the message can’t be delivered !!!
so the user might used a wrong email, or misspelled it, or the common thing which is i consider stupidity that the email is full of messages and the user usually don’t open it and use it to register in 10000 forum and mail list, and he don’t bother to open it and clean it from spam and trash mails !
this is so common in normal users who use internet for chatting and surfing unknown websites..
i saw the same problem also with some of my friends facebook mail box !
and he is a web programmer !!!!
so ppl, seriously WTF !!!
should i ask from the user to write his mobile and land line and home address so i could reply to his query ??
how i am supposed to answer him if he is not providing a working email ?!!!
i tried to write a note before the form asking from the user gently to use a valid and working email !
i will ask for mobile phones.. as his the only solution i have left in mind .. but i wish the internet user in the Arab market get mature and act responsibly with websites even i dont know how !