Lotus Notes' SMTP mail gateway can generate From: headers that contain newlines and that contain the address on the second line:

From: Full Name
        <address>

Although this is legal per RFC822, many MUAs mishandle such headers and are unable to find the address. If your site suffers from this problem, you can define the SingleLineFromHeader option using one of these forms:

O SingleLineFromHeader=bool                 configuration file (V8.8 and later) 
-OSingleLineFromHeader=bool                 command line (V8.8 and later) 
define('confSINGLE_LINE_FROM_HEADER', `bool')   mc configuration technique (V8.8 and later) 

The bool is of type Boolean. If it is true, sendmail will convert all newlines found in a From: header into space characters. If it is false, sendmail will leave all From: headers as is. The default for the mc configuration technique is false.

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