Linux – Sendmail – Sender verify failed

linuxsendmail

We are currently unable to send emails to other domains because the receiving host cannot verify the sender.

Emails are rejected with –

<<< 550-Verification failed for

<<< 550-No Such User Here

<<< 550 Sender verify failed

550 5.1.1 … User unknown

<<< 503-All RCPT commands were rejected with this error:

<<< 503-Sender verify failed

The server has been working fine up until yesterday when this problem suddenly occurred. I've tried re-booting the server and the router but that hasn't helped.

me@mycompany.co.uk does exist and is receiving emails. A check with http://verify-email.org/ returns

MX record about mycompany.co.uk exists.

Connection succeeded to mail.mycompany.co.uk SMTP.

220 server.mycompany.co.uk ESMTP Sendmail 8.14.7/8.14.1; Sat, 18 Feb 2017 09:07:24 GMT

HELO verify-email.org
250 server.mycompany.co.uk Hello verify-email.org [verify-email.org] (may be forged), pleased to meet you

MAIL FROM:
=250 2.1.0 … Sender ok

RCPT TO:
=250 2.1.5 … Recipient ok

<<< 503 Valid RCPT command must precede DATA

verify-email did report a problem last night. It was unable to connect to mail.mycompany.co.uk so connected to the secondary MX instead. I thought that might be the problem but it's connecting to mail.mycompany.co.uk now and the verification problem still exists.

Any suggestions would be greatly appreciated.

Best Answer

Since your stated problem is with sending out mail, that email verification is of no importance to you. You are going to want to verify your reverse DNS record on your outgoing IP address, make sure it exists and that ideally the domain matches the domain your email server advertises itself as. If that is good then do a blacklist check on your external IP, this can be done here:

https://mxtoolbox.com/blacklists.aspx

If its still not working verify your SPF record if you have one.

Where are the logs?

The default location depends on your linux/unix system, but the most common places are

/var/log/maillog
/var/log/mail.log
/var/adm/maillog
/var/adm/syslog/mail.log

If it's not there, look up /etc/syslog.conf. You should see something like this

mail.*         -/var/log/maillog

sendmail writes logs to the mail facility of syslog. Therefore, which file it gets written to depends on how syslog was configured.

If you system uses syslog-ng (instead of the more "traditional" syslog), then you'll have to look up your syslog-ng.conf file. You'll should something like this:

# This files are the log come from the mail subsystem.
#
destination mail     { file("/var/log/mail.log"); };
destination maillog  { file("/var/log/maillog"); };
destination mailinfo { file("/var/log/mail.info"); };
destination mailwarn { file("/var/log/mail.warn"); };
destination mailerr  { file("/var/log/mail.err"); };

Unable to send out emails?

One of the most common reason I've seen for a freshly installed sendmail not being able to send out emails is the DAEMON_OPTIONS being set to listen only on 127.0.0.1

See /etc/mail/sendmail.mc

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 #
DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl

If that's your case, remove the "Addr=127.0.0.1" part, rebuild your conf file and you're good to go!

DAEMON_OPTIONS(`Port=smtp, Name=MTA')dnl

[root@server]$ m4 sendmail.mc > /etc/sendmail.cf
[root@server]$/etc/init.d/sendmail restart

If you've been making changes to /etc/sendmail.cf manually thus far (instead of the *.m4 file) you can make similar changes in /etc/sendmail.cf. The offending line will look like this:

O DaemonPortOptions=Port=smtp,Addr=127.0.0.1, Name=MTA

Change it to:

O DaemonPortOptions=Port=smtp, Name=MTA

Nginx – configuring sendmail sender address

I think typically people use the "-f" parameter for example:

sendmail -f me@mydomain.com

Best Answer

Related Solutions

Where to check log of sendmail

Where are the logs?

Unable to send out emails?

Nginx – configuring sendmail sender address

Related Topic