550 5.5.1 protocol error

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    550 5.5.1 Protocol error

    Mar 03 17:15:55 xxxxx postfix/postscreen[20214]: PREGREET 26 after 0.04 from [xxx.xxx.xxx.xxx]:60268: EHLO MGTEXC12.xxxx.com\r\n Mar 03 17:15:55 xxxxx postfix/postscreen[20214]: NOQUEUE: reject: RCPT from [xxx.xxx.xxx.xxx]:60268: 550 5.5.1 Protocol error What is the reason I have been getting...