最简略的表达如下，请参考。
Dear Sirs:
Would you please send me a formal invitation letter for Mr. xxxx, the president of XXX company, so that we can make our visa application for our attending the conference to be held in Australia.
His passport information are as follows:
Full Name Date of birth Passport No. Occupation
Thank your for your help.
Looking forward to your reply,
Sincerely yours
（不知道现在澳洲签证需要什么形式的邀请函，如传真，PDF版还是其它规定。这需要在信件中告诉对方）
