using an email server from an external domain

[simeon_mattes]

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

1. Conecting to it, by using an email client (e.g. Thundirbird) in order to receive and send emails
2. 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:

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

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