There are two ways that sendmail can detect the end of a mail message: by noting an end-of-file (EOF) condition or by finding a line composed of a single dot. According to the SMTP and ESMTP protocols (RFC821), the end of the mail data is indicated by sending a line containing only a period. The IgnoreDots option tells sendmail to treat any line that contains only a single period as ordinary text, not as an EOF indicator.

This option is generally used from the command line when reading a message that might have a line in it that contains only a single dot. This option can safely be used in the configuration file because sendmail always turns it off (sets it to false) when reading a message using SMTP.

The forms of the i option are as follows:

O IgnoreDots=bool             configuration file (V8.7 and later) 
-OIgnoreDots=bool             command line (V8.7 and later) 
define(`confIGNORE_DOTS',bool)    mc configuration (V8.7 and later) 
-i                            command-line shorthand (deprecated) 
Oibool                        configuration file (deprecated) 
-oibool                       command line (deprecated) 

The argument bool is of type Boolean. If bool is missing, the default value is true (ignore leading dots). If the IgnoreDots option is entirely omitted, the default is false (recognize leading dots as special).

The IgnoreDots option is safe. Even if it is specified from the command line, sendmail retains its special privileges.