[cobalt-security] sendmail, POP b4 SMTP and IP addresses

[Graeme Merrall <graeme@xxxxxxxxxxxxx>]

Point me to a generic sendmail list if you feel this is to generic. 
 
Some of you may now that AOL has recently altered their mail configurations to 
cut down on spamming. There are two interesting measures they've taken. One is 
to stop accepting email from IP numbers they believe to be from subscriber DSL 
lines which forces people to use their ISP's mail server rather than running a 
mail server on their own machine which cuts down spam coming in to their 
systems. The other is to prevent reverse lookups on people with AOL 
connections so direct connections to external mail servers will generally 
fail. This helps cut down spam coming out of their systems. 
 
I actually work for AOL (and yes we use open source) and connect through 
normal AOL at home. I use Linux on my desktop and since these changes I can no 
longer use POP before SMTP as sendmail now tells me that relaying is denied as 
IP name lookup failed and there is not a AOL SMTP server for customers. If 
you're on the AOL WAN there's one but that's  
 
I've done some reading and it appears that I may be able to use either 
FEATURE(`accept_unresolvable_domains'), FEATURE(`relay_mail_from') or 
FEATURE(`delay_checks'). 
 
Two problems arise from this though. What is the best method for me to allow 
myself to send mail through the box again without compromising security and is 
it safe to go tinkering about with the m4 stuff and regenerate the sendmail.cf 
file?  If there's any sendmail people out there who can help I'd appreciate a 
few pointers 
 
Cheers, 
 Graeme