[BlueOnyx:25901] Re: sendmail issue with fairly new 5210R server

[Michael Stauber]

Hi Larry,

>    Yes, in several of the cases it happens to be two domains
> that I host (on separate BlueOnyx boxes) so I can verify
> the error from both servers - a "User unknown" for an
> existing user (that is not over quota for user or site).
> And it is only this one 5210R that is doing it.


Do you by chance run a setup where you have www.company.com on one 
server and mail.company.com on an another? There is nothing speaking 
against that and I use that setup myself.

However, when you email user at company.com from the box that has 
www.company.com you have to be careful that it doesn't try to make a 
local delivery. This is where /etc/mail/local-host-names comes in. It 
should only have entries for email aliases of Vsites or Vsite FQDNs that 
directly receive email at username at fqdn.

If these are 5210Rs and they use Sendmail, then try to switch the MTA to 
Postfix instead and see if that makes a difference.

 > Everything will work fine for hours, then suddenly
 > a single user on this domain will get the "User unknown"
 > error and that message is bounced

The Sendmail/Postfix configuration and alias setup is static and it 
doesn't change on its own unless you add/remove a user or Vsite.

So if *that* (aliases, Sendmail/Postfix config) were an issue? You'd 
have the problem *all* the time. Not once in a while or sporadically. It 
would always work or always fail hard.

The sporadic nature of the issue makes me suspect it might still be a 
DNS issue. Maybe you run or use multiple DNS servers and one has bad or 
outdated info? Then it might work as long as the "good" DNS server 
answers, but fails when the "bad" one is handling the replies.

I've had such an issue recently with the BlueOnyx mirrors and it was 
driving me mad until I realized one of my three DNS servers hadn't 
automatically update the zone in question.

-- 
With best regards

Michael Stauber