GMail accounts can and often will be temporarily suspended from usage if it appears that you are a probable spammer or spreading viruses by email or otherwise bringing harm to others and thus violating GMail's policy.
here are he quick rule book for your refrence
From: Bulk mailing using Gmail by Amit Agarwal at Digital Inspiration
Rule 1.
If you access Gmail via POP or IMAP clients (like Microsoft Outlook),
you can send an email message to a maximum of 100 people at a time.
Cross the limit and your account will be disabled for a day with the
error "550 5.4.5 Daily sending quota exceeded."
Rule 2.
If you access Gmail from the browser, you may not address an email
message to more than 500 people at a time. Try adding any more
recipients in the To, CC or BCC field and your Gmail account will get
probably disabled for 24-72 hours. Error: "Gmail Lockdown in Secton 4"
Rule 3.
Always double check email addresses of recipients before hitting the
Send button in Gmail. That's because your account will get disabled if
the email message contains a large number of non-existent or broken
addresses (<25 ?) that bounce back on failed delivery.
Rule 4:
This is slightly unrelated but still important - Google will disable
your Gmail account permanently if you don't check your Gmail email for
a period of nine months. All the stored messages will be deleted and
you Gmail address (user name) may be released for others to grab it.
In End gmail is for personal use only and if you are using it for nay kind of testing or other things suggest you to get an mail server account
here is what google says about sending limits