[ic] Strange "Unable to send mail" error

[DB]

> Hi all, i'm back and i still have got a problem with a production IC server
> :(
> 
> In fact, akopia works great but sometimes ( about 1% of error ), order email
> aren't send but order can be seen in the admin area ...
> In the /catroot/error.log i can see something the order email print there
> and as error :
> Unable to send mail
> 
> I don't see anything in the /var/log/maillog and /var/log/message.
> 
> Perhaps it's that server was loaded but i'd like to have some more infos
> about this.
> I saw in the list that someone that had got the same problem before, but i
> can't see any help reading theses posts.
> 
> IC 4.8.2
> 
> Thanks again
> David

That sounds EXACTLY like the probem I had a few weeks back. The problem 
in my case was with my DNS. The first machine listed in my 
/ets/resolv.conf was down for service. That caused sendmail to timeout 
before the DNS lookup could be performed for maybe 1 in 10 of my orders. 
Like you, I had to get the order info from the catalog's error.log. No 
errors showed up in /var/log/messages or /var/log/maillog.

Try some command line experiments using nslookup or dig to test the 
responsiveness of the first server listed in your /etc/resolv.conf, or 
try a putting different server first in the list. I strongly suspect 
your problem is related to DNS.

DB