when I type 'cat /var/spool/mail/$myUserName', I found something seems useful:
SMTP error from remote mail server after end of data: host gmail-smtp-in.l.google.com [74.125.25.26]: 550-5.7.1 [MY IP ADDR] Our system has detected an unusual rate of 550-5.7.1 unsolicited mail originating from your IP address. To protect our 550-5.7.1 users from spam, mail sent from your IP address has been blocked. 550-5.7.1 Please visit http://www.google.com/mail/help/bulk_mail.html to review 550 5.7.1 our Bulk Email Senders Guidelines. xr1si11727041pbc.309 - gsmtp
what should I do to fix it? Does adding a SPF record work?