Validating an SMTP server

Simson Garfinkel simsong at
Mon Sep 7 20:39:37 CEST 2015


Thanks for giving my tester a try.

I'm confused by your comment, though.  I was pretty sure that SMTP commands were supposed to be followed by CRLF.

Here's the quote from RFC 2821:

2.3.7 Lines

   SMTP commands and, unless altered by a service extension, message
   data, are transmitted in "lines".  Lines consist of zero or more data
   characters terminated by the sequence ASCII character "CR" (hex value
   0D) followed immediately by ASCII character "LF" (hex value 0A).
   This termination sequence is denoted as <CRLF> in this document.
   Conforming implementations MUST NOT recognize or generate any other
   character or character sequence as a line terminator.  Limits MAY be
   imposed on line lengths by servers (see section 4.5.3).

   In addition, the appearance of "bare" "CR" or "LF" characters in text
   (i.e., either without the other) has a long history of causing
   problems in mail implementations and applications that use the mail
   system as a tool.  SMTP client implementations MUST NOT transmit
   these characters except when they are intended as line terminators
   and then MUST, as indicated above, transmit them only as a <CRLF>
   sequence. <>

Am I missing something?

> On Sep 7, 2015, at 2:28 PM, Jim Popovitch <jimpop at> wrote:
> On Mon, Sep 7, 2015 at 1:02 PM, Simson Garfinkel <simsong at> wrote:
>> If you want to give my tester a try, you can try it at:
> I appears that you are using "\r\n" in your smtp test commands.   "\n"
> should be sufficient and won't cause logged errors on the systems you
> are testing.
> -Jim P.

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