-"plussed_user", when specified on the "masquerade:" line, allows a second type
-of username masquerading. If the user sets the \fB$USERPLUS\fR environment
-variable, its value will be tacked onto the actual login name, following a '+'
-sign. For instance, if I am dan@company.com, and I set \fB$USERPLUS\fR to
-"www", my mail will appear to come from "dan+www@company.com". This feature is
-meant to interact with MTA features like the one in sendmail that automatically
-delivers all mail sent to \fIuser\fR+\fIstring\fR to \fIuser\fR. One can use
-different email addresses in different situations (to aid in automatic mail
-filtering or in determining where spammers got your address) while only actually
-having a single account.
+"username_extension", when specified on the "masquerade:" line, allows a second
+type of username masquerading. If the user sets the \fB$USERNAME_EXTENSION\fR
+environment variable, its value will be appended to the actual login name. For
+instance, if I am dan@company.com, and I set \fB$USERNAME_EXTENSION\fR to
+"\-www", my mail will appear to come from "dan\-www@company.com". This is meant
+to interact with qmail's "user\-extension" feature, where mail sent to
+\fIuser\fR\-\fIstring\fR will be delivered to \fIuser\fR. Likewise, those using
+versions of sendmail for which "plussed user" processing is active can set
+\fB$USERNAME_EXTENSION\fR to "+\fIstring\fR". These MTA features are useful
+because they allow one to use different email addresses in different situations
+(to aid in automatic mail filtering or in determining where spammers got one's
+address) while only actually having a single account. Note that
+\fB$USERNAME_EXTENSION\fR is only appended to the username when \fIpost\fR is
+generating "[Resent\-]From:" lines and the SMTP envelope "From:". \fIinc\fR,
+for instance, will not try to read from a maildrop file called "dan\-www" (to
+recall the earlier example).