On Wed, Jul 14, 2004 at 11:06:16PM -0400, Gene Heskett wrote: > On Wednesday 14 July 2004 14:05, Alexander Dalloz wrote: > > [...] > > > >Of course, if Philippe did give his Sendmail a hostname which is not > >resolvable, neither by the hosts file nor a DNS, his MTA will not > > work proper. ... > All of which makes sense (I think, I'm having trouble with he > "internal" status of AAA yet) I recall reading a comment that local host names for sendmail need "enough" dots. i.e. box.bogustopdomain # will not work for some. box.subdomain.bogustopdomain # can work. Since there is a AAA.com., aaa.net. and aaa.org resolver code could be looking any of these up because you do not have enough dots. I recommend the top two levels of a private host name be researched for conflicts. I once found a nifty but flawed how-to for sendmail and dns that said use "invalid.com". It turns out that there is a registered domain by that name. Following the directions in this case did unpredictable and possibly bad things. http://www.interex.org/tech/9000/Tech/sun_hpux_interop/chap10_dns.html In part the root of this is the ndots of resolver code (not really a sendmail problem). In some cases /etc/hosts can use dots to force termination and closure. i.e. DNS resolver code should understand that a trailing dot terminates the fully qualified domain name. 22.214.171.124 boxa.aaa. boxa.aaa boxa Also "Mail -v [email protected]" may respond differently than without the trailing dot "Mail -v [email protected]". If things are correct they should be the same. Compare and contrast... host boxa.aaa. host boxa.aaa Mail -v [email protected] Mail -v [email protected] next do a reverse lookup on the host results. Forward and reverse lookup should be consistent. $ host boxa.aaa. boxa.aaa. has address 192.168.0.51 $ host 192.168.0.51 126.96.36.199.in-addr.arpa domain name pointer boxa.aaa. Since aaa is not a subdomain of a .com .net or other high level domain this dot count thing could be important. In addition sendmail has a need to locally resolve private network addresses. http://sendmail.org/tips/private-dns/ The point here is that if the reverse lookup fails for a private network as it will without local interaction mail will queue. This "should be OK" with hosts first in resolv.conf but I have not found it to be satisfactory. Also there may be issues with path MTU discovery for some ISP services. http://sendmail.org/tips/pathmtu.html It can be useful and diagnostic to force your outgoing MTU to be modestly sized. Lastly if you are on a DHCP assigned address you will find that setting up sendmail is painful. The short TTL for the domain name is a signature of dynamic DNS. Use the ISP's mail host as a smart host. This may require authentication. Set 'reply to:' headers on mail to be the ISP's assigned mail address. Collect mail from the ISP with fetchmail/ pop/ imap for local access. I once thought that MX records would be helpful but there is a window when your old IP address and DNS records could point to a different box. If that box answers then rejects mail, mail will bounce back to the sender. Summary: in etc/hosts 192.168.0.10 a.aa.priv.notpublicnet a not 192.168.0.10 a.aa a -- T o m M i t c h e l l /dev/dull where insight begins.