On Sun, 06 Jun 1999 03:03:20 EDT, "Alan S. Dobkin" <[log in to unmask]> said: > Error-Text: Mailer mxnx.berlinetz.de said: > "550 '<[log in to unmask]>SIZE=35126' > sender address target 'LISTSERV.CC.EMORY.EDU' is not a valid e-mail > domain (there is no MX record for it)." Aha. *This* wonderful flake of the DNS again. What probably happened is that the nameserfer on berlinetz.de got back a DNS reply with an empty 'Answer' section (which usually indicates a referral to the nameserver identified in the 'authority' and 'additional' sections of the reply). However, either the 'Authoritative Answer' bit was also set (which implies the hostname is valid, but no MX or A record was returned in the Answer section), or the client resolver had the 'dont recurse' bit set. The most likely culprit is the following: 'dig' reports this information on listserv.cc.emory.edu: ;; ANSWERS: listserv.cc.emory.edu. 86334 A 170.140.132.49 ;; AUTHORITY RECORDS: cc.EMORY.edu. 86334 NS ns2.EMORY.edu. cc.EMORY.edu. 86334 NS AUTH02.NS.UU.NET. cc.EMORY.edu. 86334 NS NWS-Test3.cc.EMORY.edu. cc.EMORY.edu. 86334 NS ns1.EMORY.edu. ;; ADDITIONAL RECORDS: ns2.EMORY.edu. 82014 A 170.140.2.1 AUTH02.NS.UU.NET. 157002 A 198.6.1.82 ns1.EMORY.edu. 86334 A 170.140.1.1 It's interesting that there's 4 entries in the Authority area, but only 3 A records in the Additional section. It could very well be that the berlinetz.de host chose nws-test3 as the host to recurse to, was forced to do another lookup to resolve THAT address, and got a timeout or other error. Lo and behold, there isn't an A record in the DNS for nws-test3.cc.emory.edu. Have your DNS jockeys either remove it from the NS list, or add an A record for it. Otherwise, an average of 25% of all off-campus lookups of your addresses will at best have to wait for a timeout and try one of the other 3 NS entries, or at worse will error out entirely. I've CC;ed them on this note. Valdis Kletnieks Computer Systems Senior Engineer Virginia Tech