The class printJobSettings has a method mailSubject for setting the subject of the email that gets generated, but there is no method for setting the body of the message. printJobSettings is a kernel class, so you can't modify it.
To actually send the email, the kernel passes a printJobSettings object to the method Info.ReportSendMail, which you can modify. So as a work around, pack your subject and body together in the subject, then unpack them in ReportSendMail.
In your report:
printJobSettings.mailSubject(msgSubject + '|' + msgBody);
In Info.ReportSendMail:
subjectAndBody=printJobSettings.mailSubject();
delimiterPos=strFind(subjectAndBody,'|',1,strlen(subjectAndBody));
if(delimiterPos>0)
{
msgSubject=subStr(subjectAndBody,1,delimiterPos-1);
msgBody=subStr(subjectAndBody,delimiterPos+1,strlen(subjectAndBody)-delimiterPos);
}
else
{
msgSubject=subjectAndBody;
msgBody='Axapta Report';
}