Java EE (Java Enterprise Edition) General Discussion

Can any body help me
i am using java mail API to send mail from JSP-bean.
all my program works well , but some times I get error' Access to default session denied"
and all mails, after this error ( even from a new page) does not send.
has any one exp the same error

code used
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Properties props = new Properties();
props = System.getProperties();
props.put("mail.smtp.host",smtp);
props.put("mail.smtp.auth","true");
session = javax.mail.Session.getDefaultInstance(props,null);
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is this of "System.getProperties();" or javax.mail.Session.getDefaultInstance(props,null);

Thanks in advance
Mathew