using an email server from an external domain

simeon.mattes · 03-20-2011, 04:01 AM

Hi,

I have a slackware machine which has preinstalled the sendmail mail server. For this machine I have given a domain name (I have a static IP), so I'm able to administer my email through the UI of webmin, i.e. I can send and receive emails.

However I would like to use it only as an email server, i.e. what I would like to do is

Conecting to it, by using an email client (e.g. Thundirbird) in order to receive and send emails
Conecting to it from a web server so a to send new posts etc.

By searching around I found that in order to test the mail server from outside you can use the following series of commands:

Code:

telnet mydomain 25
helo mydomain
mail from:<useremail_in_my_domain>
rcpt to:<useremail_in_external_domain>
...

However in rcpt to: I receive an error "Relaying denied".

Here is also the DNS configuration

Code:

Name	Mode	Value	Priority
domainname	A	myip	0
*.domainname	A	myip	0
mail.domainname	MX	myip	1

Any ideas, or how I could configure the email server?

Thanks in advance

ComputerErik · 03-20-2011, 11:15 AM

The reason you are getting that response is the new default behavior for any modern MTA is to not act as a relay. You will need to either allow relay based on IP or require authentication to relay. Which one is appropriate for you will all depend on where the mail server is and how you expect to connect to it.

The allow by IP is probably the easiest configuration (just add an IP or subnet to relay-domains and restart sendmail) would work fine if you will only be connecting from the same IP or small set of IPs which will not change. This might be appropriate if the mail server is behind your firewall and you will only be sending mail from within that LAN. It can also work if the server is hosted outside of your LAN but you have a static public IP and will only be sending mail from that location. Obviously this might not work so well in this day where it is common to have email on a smart phone or want to access mail from a laptop while on the road. If this is the case you will need to setup some sort of authentication mechanism (there are a few but SASL is probably the most common) so that you can relay from any IP as long as you are authenticated as a valid user.

For the receiving mail part you will probably want to look into some sort of POP3 or IMAP server such as Dovecot so you can configure the client to access the mail server and keep a copy of mail locally on your computer as well. For the web portion you will need yet another piece of software installed to give you a web interface to the mail. There are a few options, and I am not a huge fan of webmail so I have never set one up myself, but have heard Squirrel mail is a pretty good solution.

Lastly you might want to look into replacing sendmail with postfix as it is generally easier to configure and a more flexible solution.