sendmail, 4th Edition

AuthOptions

Tune authentication parameters V8.10 and later

AuthOptions provides a list of general tuning parameters that affect authentication. It is declared like this:

O AuthOptions=string                  ← configuration file (V8.10 and later)
-OAuthOptions=string                  ← configuration file (V8.10 and later)
define(`confAUTH_OPTIONS', `string')  ← mc configuration (V8.10 and later)

The argument, of type string, is a list of characters selected from those shown in Table 24-13, where each character sets a particular tuning parameter. If more than one character is listed, each character must be separated from the next by either a comma or a space.

Table 24-13. AuthOptions character settings

Character	Meaning
A	Use the AUTH= parameter from the MAIL From: command only when authentication succeeds. This character can be specified as a workaround for broken MTAs that do not correctly implement RFC2554. (Client only)
a	Provide protection from active (nondictionary) attacks during the authentication exchange. (Server only)
c	Allow only selected mechanisms (those that can pass client credentials) to be used with client credentials. (Server only)
d	Don’t permit use of mechanisms that are susceptible to passive dictionary attacks. (Server only)
f	Require forward-secrecy between sessions (where breaking one won’t help break the next). (Server only)
m	Require the use of mechanisms that support mutual authentication. (Server only) (V8.13 and above)
p	Don’t permit mechanisms to be used if they are susceptible ...