[HELP] SMTPlib not sending my mail

[ornto]

Hi, I'm trying to create an application which checks a 
dynamic web site and on certain events sends an email to me. 
My problem though is with the email task. By now I made this 
  simple test code:

#prova invio email
smtpserver = smtplib.SMTP(mailserver)
messaggio= "Messaggio di prova"
print mail
print messaggio
smtpresult=smtpserver.sendmail("Watcher",mail,messaggio)
if smtpresult:
     print smtpresult
smtpserver.quit()

"mailserver" and "mail" values are loaded from a ini file 
and they're correct.
The call to smtpserver gives back no errors (smtpresult 
remains empty).
The running enviroment gives no error.
So, it looks like that the program works alloright, sending 
the mail- BUT, I receive no mail! I've tried to change the 
smtp server with another one which still works with my isp, 
with no luck. If I try a smtp which doesn't give me access, 
I correctly receive an error from the program.
What might be the problem?