[afnog] Relay denied

[Brian Candler]

On Wed, Jul 13, 2005 at 09:38:04PM +0300, asseym at smartvisions.net wrote:
> I have found out that mail can be sent easily and normally to any address
> regardless of who hosts that domain with a flawless maillog. However when
> mail is sent by the desktop MTAs the maillog developes errors like quoted
> below---
> 
> -----------------------------------------<quote>
> Jul  4 12:24:22 ensim sendmail[6204]: j649OJqt006204: ruleset=check_rcpt,
> arg1=<asseym at yahoo.com>, relay=[193.108.254.83], re
> ject=550 5.7.1 <asseym at yahoo.com>... Relaying denied. IP name lookup
> failed [193.108.254.83]

There's your problem, right there.

The client's IP address is 193.108.254.83. sendmail has a (stupid) policy
set which says if this IP address cannot be converted to a hostname via a
reverse DNS lookup, then relaying is denied.

Your options are:
1. fix your DNS (so all your client IPs have reverse DNS, and there is
   matching forward DNS from those names back to the same IPs)
or
2. fix sendmail so it doesn't have this stupid policy (unfortunately,
   sendmail configuration is a total nightmare)
or
3. replace sendmail with a decent, modern MTA like exim or postfix,
   which can easily be configured with a sensible relaying policy

Honestly, replacing sendmail will be considerably easier than trying to fix
sendmail's config.

Regards,

Brian.