When I try a Nmap scan it shows that all ports all filtered, but how does this domain ( aspmx.l.google.com ) suppose handle all the mails if all ports are closed, when using Google Apps for businesses?
closed as too localized by Jeff Ferland, EEAA, Shane Madden, Ward, mgorven Jun 25 '12 at 2:38
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Port 25 is open to receive email via SMTP.
Your nmap result is wrong and you should be aware of the legalities of port scanning since it's a grey area in some places. Potentially, Googled detected it, and blocked you.