Specify a blank sender in SMTP communication using a Telnet client

If you ever need to specify a blank sender in the mail from command when debugging an SMTP server by using a Telnet client; use <>.
For example:
220 mta.domain.com Microsoft ESMTP MAIL Service ready at Mon, 22 Dec 2008 23:21:41 +0100
ehlo
250-mta.domain.com Hello [10.10.10.10]
250-SIZE
250-PIPELINING
250-DSN
250-ENHANCEDSTATUSCODES
250-STARTTLS
250-X-ANONYMOUSTLS
250-AUTH NTLM
250-X-EXPS GSSAPI NTLM
250-8BITMIME
250-BINARYMIME
250-CHUNKING
250-XEXCH50
250 XRDST
mail from:<>
250 2.1.0 Sender OK
This has been tested on Microsoft Exchange, maybe other mail servers will not accept it.
Update: I have recently discovered that the <> combination can be used in other SMTP verbs as well. For instance to specify that you do not want to authenticate you could send the command AUTH:<>

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