Large attachments in database mail

HI , Everyone
Please help me in dbmail while i sending a large attachment. it gives an error like this.
"The mail could not be sent to the recipients because of the mail server failure. (Sending Mail using Account 8 (2009-02-25T09:22:58). Exception Message: Cannot send mails to mail server. (The operation has timed out.). )"
Can anyone tell me how to solve this. i can send a mail with attachment upto 1mb but i cant more...
please reply me..............

EXECUTE msdb.dbo.sysmail_configure_sp
'MaxFileSize', '1073741824' ;

Thnks mr. arunyadav
for giving me reply.. but i have already change the filesize using system parameters (dabase mail wizard) . i dont know what to do ?
the error is still coming like "The mail could not be sent to the recipients because of the mail server failure. (Sending Mail using Account 8 (2009-02-27T09:15:04). Exception Message: Cannot send mails to mail server. (The operation has timed out.). )"..... please ask your coligues too.. i dont found this answer yet.....................

If you have already done this. Can you check if there are any rules in your Mail server to restrict attachment size. Just a thought..

hi , how can i check this. beacuse right now i m using the gmail account. (Gmail server) and if i m using my local smtpserver then how can i check the rules to restrict attachment size any options will be there ?????? please reply me..