sendmail and MX records when mail server is not on web host

Question

This is a problem I\'m sure is easy to fix, but I\'ve been banging my head on it all day.

I\'m developing a new web site for a client. The web site resides at (this

Answer 1

Edit the tsm.cf file (in /etc/mail/ or similar) to include

FEATURE(relay_entire_domain) 

between the DOMAIN() and MAILER() lines. Since you're editing the file, you may want to also improve security with

define(`confPRIVACY_FLAGS',``noexpn,novrfy'')

After changing the tsm.cf file (or any sendmail config file), restart or SIGHUP the sendmail process.

This change is necessary because the WWW and MX servers for the domain do not exist in the same process space; this FEATURE triggers sendmail to process messages for the domain using it's external delivery mechanism.

The edited portion of the tsm.cf file should look similar to this:

DOMAIN(website.com)dnl
FEATURE(relay_entire_domain)dnl
define(`confPRIVACY_FLAGS',``noexpn,novrfy'')dnl
MAILER(smtp)dnl
MAILER(procmail)dnl

Answer 2

Sendmail by default guesses list of local email domains. It can be turned off using the following line in your sendmail.mc file:

define(`confDONT_PROBE_INTERFACES',`True')

As root list local email domains before and after the change using:

echo '$=w' | sendmail -Am -bt

You will see which domains should be added "manually" to (usually) /etc/mail/local-host-names file after disabling auto-guessing.

After changing sendmail.mc:

1. Generate/compile new sendmail.cf file
2. Restart sendmail daemon (or send HUP signal)

Answer 3

Got stuck on the same problem. MX points to an external Exchange server but php/sendmail did not lookup this record. Instead mails posted by WordPress on this webserver dropped in the catchall-mailbox.

Solution was to delete ALL mailboxes on the webserver. Now sendmail was interested in the MX and all mails went to the Exchange.

However, the Exchange uses the webspace's mail server as SmartHost for outgoing mails. As solution for this, we were able to use the FTP credentials for accessing the mail server. I assume this solution does not work on every provider on this planet, but in our case (all-inkl.com) it worked out.

Answer 4

I think the problem is that sendmail (your process) is talking to the local sendmail daemon. The local sendmail daemon thinks that because it is website.com, it should know how to deliver the email. Unfortunately, the actual address in the to field does not exist on the web server and thus it dumps it in the "catchall" mail box. You should talk to your ISP and have them update their sendmail configuration so that mail addressed to ...@website.com gets forward to the mail exchanger instead of being handled locally.

Answer 5

What worked for me was to add an MX record on the webserver hosting the website, that points to the host assigned on the original domain name server. In the case presented here would be an mx record pointing to: mailsec.website.com

Answer 6

I'm new here. Wanted to extend RB_CWI answer, but I am not allowed to comment. His solution worked great.

You are not required to define the DOMAIN().

However, on my system I was required to install the sendmail-cf package.

The instructions below were done on CentOS 6.5

First, install sendmail-cf

sudo yum install sendmail-cf

Then, edit the senmail.mc

sudo vi /etc/mail/sendmail.mc

At the bottom of the file add FEATURE(relay_entire_domain)dnl, so it looks like:

...
FEATURE(relay_entire_domain)dnl
MAILER(smtp)dnl        # right above this line
MAILER(procmail)dnl
dnl MAILER(cyrusv2)dnl

Save the file, and restart sendmail.

sudo service sendmail restart