[nSLUG] dot issue seems to be a mailing list bug
jeff at coherentnetworksolutions.com
Wed Nov 30 20:46:37 AST 2005
On Wed, 2005-11-30 at 20:02 -0400, Donald Teed wrote:
> The SMTP server at Gmail, and my own postfix, can email a message
> a line starting with the dot and by itself (and a blank line before
> and after)
> and continue sending lines after that.
Actually telneting to nslug.ns.ca:25 and trying this out seems to
discount this theory. Likely postfix or gmail is doing something to the
message before it gets to whatever nslug is running.
> Email processed by the mailing list server is truncating the message.
> I too have used raw SMTP and know about the . used to end the message
> but that isn't what is happening in this case. It would be
> interesting to know how
> MTA + SMTP servers are normally able to ignore an instance of this.
Supprisingly, the relevent RFC seems to be of little help in providing a
general, correct, solution...
>From rfc 2821:
> 4.5.2 Transparency
> Without some provision for data transparency, the character sequence
> "<CRLF>.<CRLF>" ends the mail text and cannot be sent by the user.
> In general, users are not aware of such "forbidden" sequences. To
> allow all user composed text to be transmitted transparently, the
> following procedures are used:
> - Before sending a line of mail text, the SMTP client checks the
> first character of the line. If it is a period, one additional
> period is inserted at the beginning of the line.
> - When a line of mail text is received by the SMTP server, it checks
> the line. If the line is composed of a single period, it is
> treated as the end of mail indicator. If the first character is a
> period and there are other characters on the line, the first
> character is deleted.
> The mail data may contain any of the 128 ASCII characters. All
> characters are to be delivered to the recipient's mailbox, including
> spaces, vertical and horizontal tabs, and other control characters.
> If the transmission channel provides an 8-bit byte (octet) data
> stream, the 7-bit ASCII codes are transmitted right justified in the
> octets, with the high order bits cleared to zero. See 3.7 for
> special treatment of these conditions in SMTP systems serving a relay
> In some systems it may be necessary to transform the data as it is
> received and stored. This may be necessary for hosts that use a
> different character set than ASCII as their local character set, that
> store data in records rather than strings, or which use special
> character sequences as delimiters inside mailboxes. If such
> transformations are necessary, they MUST be reversible, especially if
> they are applied to mail being relayed.
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