sendmail configuration in RHEL
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Many times I have seen people complaining about their sendmail configuration.
So here I am going to explain configuration of sendmail on RHEL 5
NOTE: This is a simple configuration but if you want to insert some special permissions and authentications let me know I will try to help with additional info
To start of you need to check for the presence of STARTLS and SASLv2 in your machine
make sure that you install sendmail-cf because while mapping sendmail.mc into sendmail.cf you need sendmail-cf as mentioned in the configuration file
Many times I have seen people complaining about their sendmail configuration.
So here I am going to explain configuration of sendmail on RHEL 5
NOTE: This is a simple configuration but if you want to insert some special permissions and authentications let me know I will try to help with additional info
To start of you need to check for the presence of STARTLS and SASLv2 in your machine
Code:
#sendmail -d0.1 -bv root
Version 8.13.8
Compiled with: DNSMAP HESIOD HES_GETMAILHOST LDAPMAP LOG MAP_REGEX
MATCHGECOS MILTER MIME7TO8 MIME8TO7 NAMED_BIND NETINET NETINET6
NETUNIX NEWDB NIS PIPELINING SASLv2 SCANF SOCKETMAP STARTTLS
TCPWRAPPERS USERDB USE_LDAP_INIT
============ SYSTEM IDENTITY (after readcf) ============
(short domain name) $w = server
(canonical domain name) $j = server.example.com
(subdomain name) $m = example.com
(node name) $k = server.example.com
========================================================
(you should see something like this, so look for STARTTLS AND SASLv2)
Code:
#yum -y install sendmail
Code:
#rpm -qa | grep sendmail sendmail-cf-8.13.8-2.el5 sendmail-8.13.8-2.el5
Code:
#vi /etc/mail/sendmail.mc
Code:
include(`/usr/share/sendmail-cf/m4/cf.m4')dnl VERSIONID(`setup for linux')dnl ----------------------------------------> these three lines should be present OSTYPE(`linux')dnl dnl # dnl # Do not advertize sendmail version. dnl # dnl define(`confSMTP_LOGIN_MSG', `$j Sendmail; $b')dnl dnl # dnl # default logging level is 9, you might want to set it higher to dnl # debug the configuration dnl # dnl define(`confLOG_LEVEL', `9')dnl dnl # dnl # Uncomment and edit the following line if your outgoing mail needs to dnl # be sent out through an external mail server: dnl # define(`SMART_HOST', `smtp.your.provider')dnl <--------------provide the details of smtp server for me I use smtp.gmail.com define(`RELAY_MAILER_ARGS', `TCP $h 587')dnl <--------------port for relay define(`ESMTP_MAILER_ARGS', `TCP $h 587')dnl <--------------port for smtp dnl # define(`confDEF_USER_ID', ``8:12'')dnl dnl define(`confAUTO_REBUILD')dnl define(`confTO_CONNECT', `1m')dnl define(`confTRY_NULL_MX_LIST', `True')dnl define(`confDONT_PROBE_INTERFACES', `True')dnl define(`PROCMAIL_MAILER_PATH', `/usr/bin/procmail')dnl define(`ALIAS_FILE', `/etc/aliases')dnl define(`STATUS_FILE', `/var/log/mail/statistics')dnl define(`UUCP_MAILER_MAX', `2000000')dnl define(`confUSERDB_SPEC', `/etc/mail/userdb.db')dnl define(`confPRIVACY_FLAGS', `authwarnings,novrfy,noexpn,restrictqrun')dnl define(`confAUTH_OPTIONS', `A')dnl dnl # dnl # The following allows relaying if the user authenticates, and disallows dnl # plaintext authentication (PLAIN/LOGIN) on non-TLS links dnl # dnl define(`confAUTH_OPTIONS', `A p')dnl dnl # dnl # PLAIN is the preferred plaintext authentication method and used by dnl # Mozilla Mail and Evolution, though Outlook Express and other MUAs do dnl # use LOGIN. Other mechanisms should be used if the connection is not dnl # guaranteed secure. dnl # Please remember that saslauthd needs to be running for AUTH. dnl # TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl---------------------------------->uncomment this line define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl------------->uncomment this line FEATURE(`authinfo', `hash /etc/mail/auth/client-info.db')dnl------------->add this line dnl # dnl # Rudimentary information on creating certificates for sendmail TLS: dnl # cd /usr/share/ssl/certs; make sendmail.pem dnl # Complete usage: dnl # make -C /usr/share/ssl/certs usage dnl # dnl define(`confCACERT_PATH', `/etc/pki/tls/certs')dnl dnl define(`confCACERT', `/etc/pki/tls/certs/ca-bundle.crt')dnl dnl define(`confSERVER_CERT', `/etc/pki/tls/certs/sendmail.pem')dnl dnl define(`confSERVER_KEY', `/etc/pki/tls/certs/sendmail.pem')dnl dnl # dnl # This allows sendmail to use a keyfile that is shared with OpenLDAP's dnl # slapd, which requires the file to be readble by group ldap dnl # dnl define(`confDONT_BLAME_SENDMAIL', `groupreadablekeyfile')dnl dnl # dnl define(`confTO_QUEUEWARN', `4h')dnl dnl define(`confTO_QUEUERETURN', `5d')dnl dnl define(`confQUEUE_LA', `12')dnl dnl define(`confREFUSE_LA', `18')dnl define(`confTO_IDENT', `0')dnl dnl FEATURE(delay_checks)dnl FEATURE(`no_default_msa', `dnl')dnl FEATURE(`smrsh', `/usr/sbin/smrsh')dnl FEATURE(`mailertable', `hash -o /etc/mail/mailertable.db')dnl FEATURE(`virtusertable', `hash -o /etc/mail/virtusertable.db')dnl FEATURE(redirect)dnl FEATURE(always_add_domain)dnl FEATURE(use_cw_file)dnl FEATURE(use_ct_file)dnl dnl # dnl # The following limits the number of processes sendmail can fork to accept dnl # incoming messages or process its message queues to 20.) sendmail refuses dnl # to accept connections once it has reached its quota of child processes. dnl # dnl define(`confMAX_DAEMON_CHILDREN', `20')dnl dnl # dnl # Limits the number of new connections per second. This caps the overhead dnl # incurred due to forking new sendmail processes. May be useful against dnl # DoS attacks or barrages of spam. (As mentioned below, a per-IP address dnl # limit would be useful but is not available as an option at this writing.) dnl # dnl define(`confCONNECTION_RATE_THROTTLE', `3')dnl dnl # dnl # The -t option will retry delivery if e.g. the user runs over his quota. dnl # FEATURE(local_procmail, `', `procmail -t -Y -a $h -d $u')dnl FEATURE(`access_db', `hash -T<TMPF> -o /etc/mail/access.db')dnl-------------------->uncomment FEATURE(`blacklist_recipients')dnl EXPOSED_USER(`root')dnl dnl # dnl # For using Cyrus-IMAPd as POP3/IMAP server through LMTP delivery uncomment dnl # the following 2 definitions and activate below in the MAILER section the dnl # cyrusv2 mailer. dnl # dnl define(`confLOCAL_MAILER', `cyrusv2')dnl dnl define(`CYRUSV2_MAILER_ARGS', `FILE /var/lib/imap/socket/lmtp')dnl dnl # dnl # The following causes sendmail to only listen on the IPv4 loopback address dnl # 127.0.0.1 and not on any other network devices. Remove the loopback dnl # address restriction to accept email from the internet or intranet. dnl # dnl # DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl DAEMON_OPTIONS(`Port=smtp, Name=MTA')dnl------------------------>remove loopback address dnl # dnl # The following causes sendmail to additionally listen to port 587 for dnl # mail from MUAs that authenticate. Roaming users who can't reach their dnl # preferred sendmail daemon due to port 25 being blocked or redirected find dnl # this useful. dnl # DAEMON_OPTIONS(`Port=submission, Name=MSA, M=Ea')dnl -------------------->uncomment dnl # dnl # The following causes sendmail to additionally listen to port 465, but dnl # starting immediately in TLS mode upon connecting. Port 25 or 587 followed dnl # by STARTTLS is preferred, but roaming clients using Outlook Express can't dnl # do STARTTLS on ports other than 25. Mozilla Mail can ONLY use STARTTLS dnl # and doesn't support the deprecated smtps; Evolution <1.1.1 uses smtps dnl # when SSL is enabled-- STARTTLS support is available in version 1.1.1. dnl # DAEMON_OPTIONS(`Port=smtps, Name=TLSMTA, M=s')dnl --------------------->uncomment dnl # dnl # The following causes sendmail to additionally listen on the IPv6 loopback dnl # device. Remove the loopback address restriction listen to the network. dnl # dnl DAEMON_OPTIONS(`port=smtp,Addr=::1, Name=MTA-v6, Family=inet6')dnl dnl # dnl # enable both ipv6 and ipv4 in sendmail: dnl # dnl DAEMON_OPTIONS(`Name=MTA-v4, Family=inet, Name=MTA-v6, Family=inet6') dnl # dnl # We strongly recommend not accepting unresolvable domains if you want to dnl # protect yourself from spam. However, the laptop and users on computers dnl # that do not have 24x7 DNS do need this. dnl # FEATURE(`accept_unresolvable_domains')dnl dnl # dnl FEATURE(`relay_based_on_MX')dnl dnl # dnl # Also accept email sent to "localhost.localdomain" as local email. dnl # LOCAL_DOMAIN(`localhost.localdomain')dnl dnl # dnl # The following example makes mail from this host and any additional dnl # specified domains appear to be sent from mydomain.com dnl # MASQUERADE_AS(`mydomain.com')dnl -----------------> write your domain and uncomment dnl # dnl # masquerade not just the headers, but the envelope as well dnl # dnl FEATURE(masquerade_envelope)dnl dnl # dnl # masquerade not just @mydomainalias.com, but @*.mydomainalias.com as well dnl # dnl FEATURE(masquerade_entire_domain)dnl dnl # dnl MASQUERADE_DOMAIN(localhost)dnl dnl MASQUERADE_DOMAIN(localhost.localdomain)dnl dnl MASQUERADE_DOMAIN(mydomainalias.com)dnl dnl MASQUERADE_DOMAIN(mydomain.lan)dnl MAILER(smtp)dnl
Code:
#cd /etc/mail/auth #vi client-info AuthInfo:(smtp_server)(for me gmail.com) "U:username" "P:Password" "M:PLAIN" AuthInfo: "U:username" "P:Password" "M:PLAIN"
Code:
#makemap -r hash client-info.db < client-info
Code:
#vi /etc/mail/access Connect:your-ip RELAY
Code:
#m4 sendmail.mc > sendmail.cf
Code:
#service sendmail restart
Code:
#sendmail -v user@domain.com
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