Sendmail issues "530 Authentication required" error message when authinfo is supplied

sender_email - email address that does not exist, but must be used as FROM address, because receiver host rejects emails from other emails. receiver_email - email that is supposed to receive the sent message local_smtp - SMTP server that is installed on another computer in the local network and forwards all received messages to external_smtp external_smtp - SMTP server that is installed on a computer in another network and rejects all emails that do not come from sender_email I have configured sendmail to send emails from sender_email and authenticate with user/password to local_smtp that is supposed to send the email message further to external_smtp that only accepts emails sent from a specific email, which is sender_email in this case. However, judging from the log files sendmail authenticates with external_smtp instead of local_smtp. I do not want to authenticate with external_smtp, because that is up to local_smtp. logfile: 10745 >> EHLO mgmt-snmp 10759 >> MAIL From: AUTH=sender_email 10759 >> This is a MIME-encapsulated message 10759 >>> 10759 >>> --t8IEdmbX010759.1442587188/mgmt-snmp 10759 >>> 10759 >>> The original message was received at Fri, 18 Sep 2015 16:39:48 +0200 10759 >>> from root@localhost 10759 >>> 10759 >>> ----- The following addresses had permanent fatal errors ----- 10759 >>> receiver_email 10759 >>> (reason: 530 authentication required) 10759 >>> I guess it has something to do with AUTH=sender_email, but I do not know how to change it. sendmail.mc: divert(-1)dnl #----------------------------------------------------------------------------- # $Sendmail: debproto.mc,v 8.14.4 2014-02-11 13:02:08 cowboy Exp $ # # Copyright (c) 1998-2010 Richard Nelson. All Rights Reserved. # # cf/debian/sendmail.mc. Generated from sendmail.mc.in by configure. # # sendmail.mc prototype config file for building Sendmail 8.14.4 # # Note: the .in file supports 8.7.6 - 9.0.0, but the generated # file is customized to the version noted above. # # This file is used to configure Sendmail for use with Debian systems. # # If you modify this file, you will have to regenerate /etc/mail/sendmail.cf # by running this file through the m4 preprocessor via one of the following: # * make (or make -C /etc/mail) # * sendmailconfig # * m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf # The first two options are preferred as they will also update other files # that depend upon the contents of this file. # # The best documentation for this .mc file is: # /usr/share/doc/sendmail-doc/cf.README.gz # #----------------------------------------------------------------------------- divert(0)dnl # # Copyright (c) 1998-2005 Richard Nelson. All Rights Reserved. # # This file is used to configure Sendmail for use with Debian systems. # define(`_USE_ETC_MAIL_')dnl include(`/usr/share/sendmail/cf/m4/cf.m4')dnl VERSIONID(`$Id: sendmail.mc, v 8.14.4-4.1ubuntu1 2014-02-11 13:02:08 cowboy Exp $') OSTYPE(`debian')dnl DOMAIN(`debian-mta')dnl dnl # Items controlled by /etc/mail/sendmail.conf - DO NOT TOUCH HERE undefine(`confHOST_STATUS_DIRECTORY')dnl #DAEMON_HOSTSTATS= dnl # Items controlled by /etc/mail/sendmail.conf - DO NOT TOUCH HERE dnl # dnl # General defines dnl # dnl # SAFE_FILE_ENV: [undefined] If set, sendmail will do a chroot() dnl # into this directory before writing files. dnl # If *all* your user accounts are under /home then use that dnl # instead - it will prevent any writes outside of /home ! dnl # define(confSAFE_FILE_ENV', ')dnl dnl # dnl # Daemon options - restrict to servicing LOCALHOST ONLY !!! dnl # Remove `, Addr=' clauses to receive from any interface dnl # If you want to support IPv6, switch the commented/uncommentd lines dnl # FEATURE(`no_default_msa')dnl dnl DAEMON_OPTIONS(`Family=inet6, Name=MTA-v6, Port=smtp, Addr=::1')dnl DAEMON_OPTIONS(`Family=inet, Name=MTA-v4, Port=smtp')dnl dnl DAEMON_OPTIONS(`Family=inet6, Name=MSP-v6, Port=submission, M=Ea, Addr=::1')dnl DAEMON_OPTIONS(`Family=inet, Name=MSP-v4, Port=submission, M=Ea, Addr=127.0.0.1')dnl dnl # dnl # Be somewhat anal in what we allow define(`confPRIVACY_FLAGS',dnl `needmailhelo,needexpnhelo,needvrfyhelo,restrictqrun,restrictexpand,nobodyreturn,authwarnings')dnl dnl # dnl # Define connection throttling and window length define(confCONNECTION_RATE_THROTTLE', 15')dnl define(confCONNECTION_RATE_WINDOW_SIZE',10m')dnl dnl # dnl # Features dnl # dnl # use /etc/mail/local-host-names FEATURE(`use_cw_file')dnl dnl # dnl # The access db is the basis for most of sendmail's checking FEATURE(access_db', , skip')dnl dnl # dnl # The greet_pause feature stops some automail bots - but check the dnl # provided access db for details on excluding localhosts... FEATURE(greet_pause', 1000')dnl 1 seconds dnl # dnl # Delay_checks allows senderrecipient checking FEATURE(delay_checks', friend', `n')dnl dnl # dnl # If we get too many bad recipients, slow things down... define(confBAD_RCPT_THROTTLE',3')dnl dnl # dnl # Stop connections that overflow our concurrent and time connection rates FEATURE(conncontrol', nodelay', `terminate')dnl FEATURE(ratecontrol', nodelay', `terminate')dnl dnl # dnl # If you're on a dialup link, you should enable this - so sendmail dnl # will not bring up the link (it will queue mail for later) dnl define(confCON_EXPENSIVE',True')dnl dnl # dnl # Dialup/LAN connection overrides dnl # include(`/etc/mail/m4/dialup.m4')dnl include(`/etc/mail/m4/provider.m4')dnl dnl LOCAL_CONFIG dnl EXPOSED_USER(root uucp)dnl # users exempt from masquerading dnl LOCAL_USER(root)dnl dnl MASQUERADE_AS(`external_smtp')dnl dnl FEATURE(`allmasquerade')dnl dnl FEATURE(`masquerade_envelope')dnl dnl FEATURE(`nullclient', local_smtp)dnl LOCAL_CONFIG ## Custom configurations below (will be preserved) define(SMART_HOST', local_smtp')dnl define(confAUTH_MECHANISMS', EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl FEATURE(authinfo', hash /etc/mail/authinfo')dnl define(RELAY_MAILER_ARGS', TCP $h 25')dnl dnl # dnl # Default Mailer setup MAILER_DEFINITIONS MAILER(`local')dnl MAILER(`smtp')dnl authinfo: AuthInfo:local_smtp "U:root" "I:my_username" "P:my_password"