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When sending out email to xxx@terremark.com through my own SMTP server (mail.sarit.be), the receiving mail server replies with:

451 #4.1.8 Domain of sender address <xxx@sarit.be> does not resolve

Judging from my postfix log, all of the receiving MX server are unable to resolve sarit.be or mail.sarit.be.

;; QUESTION SECTION:
;terremark.com.         IN  MX

;; ANSWER SECTION:
terremark.com.      300 IN  MX  15 fldsmtpe04.verizon.com.
terremark.com.      300 IN  MX  15 fldsmtpe01.verizon.com.
terremark.com.      300 IN  MX  15 fldsmtpe02.verizon.com.
terremark.com.      300 IN  MX  15 fldsmtpe03.verizon.com.

Aug  6 08:47:42 charlie postfix/smtp[22257]: 2A45D2D56: to=<xxx@terremark.com>, relay=fldsmtpe01.verizon.com[140.108.26.140]:25, delay=418619, delays=418496/0.01/63/60, dsn=4.0.0, status=deferred (host fldsmtpe01.verizon.com[140.108.26.140] said: 451 #4.1.8 Domain of sender address <xxx@sarit.be> does not resolve (in reply to MAIL FROM command))
Aug  6 09:56:41 charlie postfix/smtp[22866]: 2A45D2D56: host fldsmtpe02.verizon.com[140.108.26.141] said: 451 #4.1.8 Domain of sender address <xxx@sarit.be> does not resolve (in reply to MAIL FROM command)
Aug  6 09:57:44 charlie postfix/smtp[22866]: 2A45D2D56: to=<xxx@terremark.com>, relay=fldsmtpe03.verizon.com[140.108.26.142]:25, delay=422821, delays=422697/0.01/64/60, dsn=4.0.0, status=deferred (host fldsmtpe03.verizon.com[140.108.26.142] said: 451 #4.1.8 Domain of sender address <xxx@sarit.be> does not resolve (in reply to MAIL FROM command))
Aug  6 11:06:42 charlie postfix/smtp[23660]: 2A45D2D56: host fldsmtpe01.verizon.com[140.108.26.140] said: 451 #4.1.8 Domain of sender address <xxx@sarit.be> does not resolve (in reply to MAIL FROM command)
Aug  6 11:07:44 charlie postfix/smtp[23660]: 2A45D2D56: to=<xxx@terremark.com>, relay=fldsmtpe03.verizon.com[140.108.26.142]:25, delay=427021, delays=426897/0.01/64/60, dsn=4.0.0, status=deferred (host fldsmtpe03.verizon.com[140.108.26.142] said: 451 #4.1.8 Domain of sender address <xxx@sarit.be> does not resolve (in reply to MAIL FROM command))
Aug  6 12:16:42 charlie postfix/smtp[24312]: 2A45D2D56: host fldsmtpe04.verizon.com[140.108.26.143] said: 451 #4.1.8 Domain of sender address <xxx@sarit.be> does not resolve (in reply to MAIL FROM command)
Aug  6 12:17:43 charlie postfix/smtp[24312]: 2A45D2D56: to=<xxx@terremark.com>, relay=fldsmtpe02.verizon.com[140.108.26.141]:25, delay=431221, delays=431097/0.01/63/60, dsn=4.0.0, status=deferred (host fldsmtpe02.verizon.com[140.108.26.141] said: 451 #4.1.8 Domain of sender address <xxx@sarit.be> does not resolve (in reply to MAIL FROM command))
Aug  6 13:26:42 charlie postfix/smtp[24956]: 2A45D2D56: host fldsmtpe02.verizon.com[140.108.26.141] said: 451 #4.1.8 Domain of sender address <xxx@sarit.be> does not resolve (in reply to MAIL FROM command)
Aug  6 13:27:43 charlie postfix/smtp[24956]: 2A45D2D56: to=<xxx@terremark.com>, relay=fldsmtpe04.verizon.com[140.108.26.143]:25, delay=435420, delays=435297/0.01/63/60, dsn=4.0.0, status=deferred (host fldsmtpe04.verizon.com[140.108.26.143] said: 451 #4.1.8 Domain of sender address <xxx@sarit.be> does not resolve (in reply to MAIL FROM command))
Aug  8 08:21:34 charlie postfix/smtp[15495]: 46D6E6353: host fldsmtpe03.verizon.com[140.108.26.142] said: 451 #4.1.8 Domain of sender address <xxx@sarit.be> does not resolve (in reply to MAIL FROM command)

I have verified the reverse DNS lookup of my MX server and the SPF record for the sarit.be domain.

;; QUESTION SECTION:
;sarit.be.          IN  MX
;; ANSWER SECTION:
sarit.be.       3600    IN  MX  10 mail.sarit.be.

;; QUESTION SECTION:
;mail.sarit.be.         IN  A
;; ANSWER SECTION:
mail.sarit.be.      2128    IN  A   176.9.7.243

;; QUESTION SECTION:
;243.7.9.176.in-addr.arpa.  IN  PTR
;; ANSWER SECTION:
243.7.9.176.in-addr.arpa. 43200 IN  PTR mail.sarit.be.

;; QUESTION SECTION:
;sarit.be.          IN  SPF
;; ANSWER SECTION:
sarit.be.       3600    IN  SPF "v=spf1 +a +mx ~all"

Finally, I tcpdumped the SMTP traffic between my own mail server and the other MX server:

220 fldsmtpe01.verizon.com ESMTP
EHLO mail.sarit.be
250-fldsmtpe01.verizon.com
250-8BITMIME
250-SIZE 20971520
250 STARTTLS
MAIL FROM:<xxx@sarit.be> SIZE=537
451 #4.1.8 Domain of sender address <xxx@sarit.be> does not resolve
RSET
250 reset
QUIT
221 fldsmtpe01.verizon.com

I don't see anything wrong with my DNS stuff. I have no trouble sending email to other domains. It's easy to think that the error is on the receiving mail server. What do you think?

PS: The reverse DNS thing doesn't seem all that important in this case because when I send mail from xxx@telenet.be to xxx@terremark.com, the email is accepted even if the forward/reverse lookup for those MX servers does not match.

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1 Answer

up vote 1 down vote accepted

This looks like a temporary DNS issue on receiving side. Their server just can't resolve your address for some reason. I think nothing can be done to fix that on your side. Probably you should contact their representative using another email and ask them to address this issue.

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it probably was, problem is solved now –  user131368 Aug 10 '12 at 10:28
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