since many isp's don't allow residential isp's to send out emails, i want to use my isp's native smtp server (smtp-server.hot.rr.com) to send out emails with sendmail; i don't know where/how to configure this, though....

i know that roadrunner and many other isp's are supposed to block outgoing on port 25, but i want to try nonetheless

thx in advance!

You will need to add a line like this to sendmail.mc:
define(`SMART_HOST',`smtp.yourisp.com')

The remake sendmail.cf (you might want to make a backup first):
m4 /etc/mail/sendmail.mc > /etc/sendmail.cf

After you restart sendmail it should use your ISPs smtp server as relay.

I've not heard of many ISPs blocking all outgoing SMTP - they will at least let you reach their server.

hmm, didn't work; i successfully created the .cf file, but afaik, the roadrunner smtp server was not being used; when i try to email people at services like roadrunnner or aol, i get a mailer-daemon notice telling me that their services reject dynamic/residential IP e-mail transactions

web-based mail like yahoo and hotmail work perfectly, though

here is the mail i get when emailing roadrunner accounts:

(edited out: don't want people too many people to see this info just yet; the e-mail you will see if you try to send mail with a residential ip will be pretty distinct)

perhaps i'm looking at the wrong thing... it is the fact that i'm using my own smtp server that is causing problems, right?

awesome, i think i've got this sorted out

first, it Was the smtp server that was causing the problem; if you don't use a business-class mail transfer protocol/ip, then many isp's will reject the e-mail

however, instead of using localhost as the transfer program, just use the native isp server by editing you sendmail.cf file (for slackware it is in /etc/mail) and looking for this line:

# "Smart" relay host (may be null)
DS

and append the correct server right next to DS (no spaces); so for roadrunner you can use

# "Smart" relay host (may be null)
DSsmtp-server.hot.rr.com

and it will work! i am sending to aol and roadrunner users with no problems

no authentication required, it seems, since the only people who can access that are the actual roadrunner subscribers

also, in regards to your isp's blocking your ability to do this: usually only if you are a spammer or a big-time p2p user will they block port 25 usage for mail servers

That is what editing the sendmail.mc fils should do but i gave you the wrong path to sendmail.cf - sorry.