+.PP
+If
+.B nmh
+has been compiled with OAuth support, the
+.B \-saslmech xoauth2
+switch will enable OAuth authentication. The
+.B \-user
+switch must be used, and the
+.I user-name
+must be an email address the user has for the service, which must
+be specified with the
+.B \-authservice
+.I service
+switch. Before using this, the user must authorize nmh by running
+.B mhlogin
+and grant authorization to that account. See the
+.B mhlogin
+man page for more details.
+.PP
+Gmail only supports POP3 over TLS, but
+.B msgchk
+has no TLS support. To work around this, use something like
+.B -proxy 'openssl s_client -connect %h:995 -CAfile /etc/ssl/certs/ca-certificates.crt -quiet'