Sender domain must resolve problem

[Len Conrad]

>Running /var/spool/mqueue/e9BDifO26131 (sequence 2 of 2)
><techexpo at techexpo.com>... Connecting to mail.techexpo.com. via esmtp...
>220 cb013.irv.concentric.net ESMTP Sendmail 8.9.3/8.9.3; Thu, 12 Oct
>2000 08:13:13 -0700
> >>> EHLO styx.rtds.com
>250-cb013.irv.concentric.net Hello userSd087.videon.wave.ca
>[207.161.225.107], pleased to meet you
>250-8BITMIME
>250-SIZE 7340032
>250-DSN
>250-ONEX
>250-XUSR
>250 HELP
> >>> MAIL From:<rjd at rtds.com> SIZE=7931
>451 <rjd at rtds.com>... Sender domain must resolve
><techexpo at techexpo.com>... Deferred: 451 <rjd at rtds.com>... Sender domain
>must resolve

sender domain is the MAIL FROM: <sender at senderdomain>

rtds.com has no A record:

# dig rtds.com a

; <<>> DiG 8.2 <<>> rtds.com a
;; res options: init recurs defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; QUERY SECTION:
;;      rtds.com, type = A, class = IN

;; AUTHORITY SECTION:
rtds.com.               1h34m35s IN SOA  dns1.mts.net. domreg.escape.ca. (
                                         2000072402      ; serial
                                         3H              ; refresh
                                         30M             ; retry
                                         1W              ; expiry
                                         1D )            ; minimum





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