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Old 03-29-2014, 05:16 AM   #1
bennetthaselton
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Registered: Dec 2010
Posts: 12

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sendmail denies relaying, "Cannot resolve PTR"


I am trying to migrate my website and mail server to a new VPS at the IP address 65.181.125.58. To test whether receiving mail is set up correctly, I used my third-party server 66.90.104.230 and tried telnetting to 65.181.125.58 port 25 to send mail, but I got the error "Relaying temporarily denied. Cannot resolve PTR record for 66.90.104.230":

[root@local ~]# telnet 65.181.125.58 25
Trying 65.181.125.58...
Connected to 65.181.125.58 (65.181.125.58).
Escape character is '^]'.
220 www.peacefire.org ESMTP Sendmail 8.13.8/8.13.8; Sat, 29 Mar 2014 05:13:19 -0
400
HELO mousematrix.com
250 www.peacefire.org Hello [66.90.104.230], pleased to meet you
MAIL FROM: tester@mousematrix.com
250 2.1.0 tester@mousematrix.com... Sender ok
RCPT TO: bennett@peacefire.org
450 4.4.0 bennett@peacefire.org... Relaying temporarily denied. Cannot resolve PTR record for 66.90.104.230

The odd thing is that I've found multiple sources claiming that sendmail "by default doesn't deny relaying based on a missing PTR record", e.g.:
http://objectmix.com/sendmail/211946...ing-relay.html

but here that's exactly what sendmail is doing even though I haven't changed any options. How do I get it to stop?

I don't want to set up a PTR record for 66.90.104.230, I want to make sure the new VPS accepts mail from IPs without a PTR record since that's the way the old VPS worked and I can't risk causing any breakages by changing the way mail is handled.

Below is my exact sendmail.mc file. Note in particular the line

FEATURE(`accept_unresolvable_domains')dnl

which made me think I definitely wasn't supposed to get this error.

---

divert(-1)dnl
dnl #
dnl # This is the sendmail macro config file for m4. If you make changes to
dnl # /etc/mail/sendmail.mc, you will need to regenerate the
dnl # /etc/mail/sendmail.cf file by confirming that the sendmail-cf package is
dnl # installed and then performing a
dnl #
dnl # make -C /etc/mail
dnl #
include(`/usr/share/sendmail-cf/m4/cf.m4')dnl
VERSIONID(`setup for linux')dnl
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 #
dnl define(`SMART_HOST', `smtp.your.provider')dnl
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 #
dnl TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
dnl define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
dnl #
dnl # Rudimentary information on creating certificates for sendmail TLS:
dnl # cd /etc/pki/tls/certs; make sendmail.pem
dnl # Complete usage:
dnl # make -C /etc/pki/tls/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
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
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 #
dnl DAEMON_OPTIONS(`Port=submission, Name=MSA, M=Ea')dnl
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 #
dnl # For this to work your OpenSSL certificates must be configured.
dnl #
dnl DAEMON_OPTIONS(`Port=smtps, Name=TLSMTA, M=s')dnl
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 #
dnl MASQUERADE_AS(`mydomain.com')dnl
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
MAILER(procmail)dnl
dnl MAILER(cyrusv2)dnl
 
Old 03-30-2014, 03:46 AM   #2
bathory
LQ Guru
 
Registered: Jun 2004
Location: Piraeus
Distribution: Slackware
Posts: 12,827

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Hi.

You can add 66.90.104.230 in /etc/mail/access
Code:
66.90.104.230 RELAY
and rebuild the access database
Code:
makemap hash etc/mail/access < etc/mail/access
 
Old 03-30-2014, 12:34 PM   #3
bennetthaselton
LQ Newbie
 
Registered: Dec 2010
Posts: 12

Original Poster
Rep: Reputation: 0
Quote:
Originally Posted by bathory View Post
Hi.

You can add 66.90.104.230 in /etc/mail/access
Code:
66.90.104.230 RELAY
and rebuild the access database
Code:
makemap hash etc/mail/access < etc/mail/access
Do you mean
Code:
makemap hash etc/mail/access.db < etc/mail/access
?
 
Old 03-30-2014, 02:09 PM   #4
bathory
LQ Guru
 
Registered: Jun 2004
Location: Piraeus
Distribution: Slackware
Posts: 12,827

Rep: Reputation: 1866Reputation: 1866Reputation: 1866Reputation: 1866Reputation: 1866Reputation: 1866Reputation: 1866Reputation: 1866Reputation: 1866Reputation: 1866Reputation: 1866
Quote:
Originally Posted by bennetthaselton View Post
Do you mean
Code:
makemap hash etc/mail/access.db < etc/mail/access
?
No. But I've missed the leading slash "/" of the path to the access database:
Code:
makemap hash /etc/mail/access < /etc/mail/access
 
Old 03-30-2014, 03:07 PM   #5
bennetthaselton
LQ Newbie
 
Registered: Dec 2010
Posts: 12

Original Poster
Rep: Reputation: 0
Quote:
Originally Posted by bathory View Post
No. But I've missed the leading slash "/" of the path to the access database:
Code:
makemap hash /etc/mail/access < /etc/mail/access
Oh OK I thought the command would overwrite the /etc/mail/access file; I didn't realize the command automatically appended ".db" to the name of the output file (since that's not in the man page...).

In any case the solution turned out to be something else -- sendmail was giving an error about PTR records but the actual problem had nothing to do with PTR records, it was because sendmail didn't realize bennett@peacefire.org was a local address so it was trying to relay it instead of accept it for local delivery. (On the old VPS that I was migrating from, the hostname was stored "peacefire.org" so sendmail implicitly accepted mail for @peacefire.org addresses; on the new VPS it was stored as "www.peacefire.org", and that difference introduced the problem.) Added peacefire.org to /etc/mail/local-host-names and restarted sendmail and that seemed to fix it.
 
  


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