Sendmail server, as aclient of SMTP auth

[kcpant]

HI friends,

one of my site is using linux based sendmail server for local (intranet) mailing, and external mails are routed (relayed) through a smart host, which is a mail service provider for this customer. 2-3 days ago, the mail service provider has been changed, and new service provider's smtp requires authentication (smtp auth).now, I have configured sendmail to act as a client when relaying mails outside through new smart host, and used feature 'authinfo'. I made a database file for authinfo credentials (user name, password etc).
Now, I have some confusion about this authinfo feature. mails can be sent outside by sendmail through sendmail sent by all users, even I make entries for only one user in authinfo database file. It means, the smart host's smtp server only checkes for authenticated user, it doesn't checks weather the mail sent is sent by the same user or anybody else.I need your sugetion in this regard,
1. Is using only one user's credentials in authinfo file for sending all users mails out has any problem or not...
2. is using only one user's credential will compromise the throuput of outgoing mails ( I mean, if I use more user's credentials, will the mails go simultaneously out by logging in all the users specified in authinfo database)...
3. is there any way without using authinfo feature, to facilitate authinfo to the smart host automatically.

thanks in advance..

[Gopi Sekar]

I am not sendmail expert, but here are my inputs anyway ...

1. Having only one user credential and using that to forward all local mails to relay server is not a good choice, because if a hacker can get hold of your sendmail server then he can use it to send spam mails by having different from names. Best would be to use the combination of both credentials to validate and user name to verify user name is same as the one which is validated, this way no internal user can also send mail masquarding as another user.

2. credentials are only used for authentication, it is equivalent to your /etc/passwd. so as long as sendmail can fork a thread and service a mail there should not be any throughput problem

3. I dunno :)

Gopi