Hi all,

I have following situation:

my mailserver has
CentOS 5.2
sendmail 8.13.8

mail server contains mail accounts with, lets say (user)@company.com accounts. Everyone inside same network as mail server, can send mail to local accounts and external accounts.

However if user is using mail (outlook as client) from outside the network mail server, he/she can send mail to local users ((user)@company.com) but not to outside addresses ((user)@anothercompany.com) receiving relaying denied error.

I found out that this is quite safe situation against spammers, but it makes mailing difficult for people who cannot get into same network as server.

How could SMTP usage be authenticated and allowed by sender, who has mail account on my mail server (could it be username and password like used on receiving mail)?

I found out that IP addresses can be allowed to be relayed but the problem there is, that you never know beforehand from which ip the user is currently connecting from (home, friend's home, etc...). So this does not work. Also allowing list of recipents does not work here since mail should be allowed to send to any mail domain.

I assume some kind of secure connection (as in outlook it can be checked) is also needed when mail is coming from outside mail server's network. How can this be done?

Thank you for your time.

Yes, SMTP AUTH is what you need.

http://www.sendmail.org/~ca/email/auth.html will get you started.

Thank you for directing me on right way.