This is from RFC 821 (base SMTP RFC).
Joel
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.
1. Before sending a line of mail text the sender-SMTP checks
the first character of the line. If it is a period, one
additional period is inserted at the beginning of the line.
2. When a line of mail text is received by the receiver-SMTP
it checks the line. If the line is composed of a single
period it is the end of mail. 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 format effectors and other control characters. If
the transmission channel provides an 8-bit byte (octets) data
stream, the 7-bit ASCII codes are transmitted right justified
in the octets with the high order bits cleared to zero.
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, or that store data in records rather than
strings. If such transforms are necessary, they must be
reversible -- especially if such transforms are applied to
mail being relayed.
On Tue, Oct 23, 2001 at 09:08:39AM -0700, Peter Jay Salzman wrote:
> always wanted to know this little tidbit:
>
> when sending email, what happens when you send a period on a line all by
> itself? like this:
>
> .
>
> what does the MTA do to make sure the email doesn't end prematurely?
>
> pete
>
> --
> "You may not use the Software in connection with any site that disparages
> Microsoft, MSN, MSNBC, Expedia, or their products or services ..."
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