about Send JavaMail

I write a program in my servlet to sendmail, at end of send mail:

I use Transport.send(message);

there are no exceptions and the mail session debug shows that 250 OK was returned.

but I didn't receive any mails

but if I change Transport.send(message);

to the follows

Transport transport = getMailSession().getTransport("smtp");

transport.connect("smtp.mail.yahoo.co.jp","user","pass");

transport.sendMessage(message, message.getAllRecipients());

transport.close();

I soon receive the sent mails.

can anyone explain this? I think it is right of the two method, but the former the smtp server queueed my mails,

[786 byte] By [okoi80a] at [2007-11-27 1:33:34]