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Sendmail, 3rd Edition by Bryan Costales

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Name

BlankSub

Synopsis

Some mailer programs have difficulty handling addresses that contain spaces. Such addresses are both illegal under RFC2821 and RFC2822 and subject to gross misinterpretation. For example, the address:

John Q Public@wash.dc.gov     decidedly not kosher

is viewed by some MUA programs as being composed of three separate addresses: John, Q, and Public@wash.dc.gov. To prevent this misinterpretation, such MUAs usually either quote the user portion or escape each space with a backslash:

"John Q Public"@wash.dc.gov     quoted
John\ Q\ Public@wash.dc.gov escaped

The BlankSub option is intended to handle an address that contains internal spaces, and is neither quoted nor escaped. For sendmail a space is any character defined by the C-language library routine isspace(3).

Most sites use a . (dot or period) or an _ (underscore) character to replace unquoted space characters. That is, they declare the BlankSub option as one of the following:

O BlankSub=.
O BlankSub=_

Feeding the address:

John Q Public@wash.dc.gov

through sendmail with the option BlankSub set to a dot yields:

John.Q.Public@wash.dc.gov

The forms of the BlankSub option are as follows:

O BlankSub=char             configuration file (V8.7 and later) 
-OBlankSub=char             command line (V8.7 and later) 
define(`confBLANK_SUB',char)    mc configuration (V8.7 and later) 
OBchar                      configuration file (deprecated) 
-oBchar command line (deprecated) 

The argument char is of type character and is a single character. The default, if this option ...

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