mail error

[sweetz]

I have a client wich cannot send mail to a particular email address (generic=office@destination.tld)
The error is like this:

Dec 14 15:59:29 web1 postfix/smtp[15910]: 80D3B16B809F: to=<office@destination.tld>, relay=mail.destination.tld[xx.xx.xx.170]:25, delay=1993, delays=1973/0.01/1.2/19, dsn=4.0.0, status=deferred (host mail.destination.tld[xx.xx.xx.170] said: 451 SPF lookup failure (#4.3.0) (in reply to MAIL FROM command))

the senders domain file looks like this:

$TTL 86400
@ IN SOA xx.xxx.135.92. admin.sender.tld. (
2007121402 ; serial, todays date + todays serial #
28800 ; refresh, seconds
7200 ; retry, seconds
604800 ; expire, seconds
86400 ) ; minimum, seconds
;
NS xx.xxx.135.92. ; Inet Address of name server 1
NS xx.xxx.135.91. ; Inet Address of name server 2
;

mx MX 10 mail.sender.tld.

sender.tld. A xx.xxx.166.10
www A xx.xxx.166.10
ftp A xx.xxx.166.10
mail A xx.xxx.166.10

pop3 CNAME mail.sender.tld.
smtp CNAME mail.sender.tld.

sender.tld. TXT "v=spf1 a mx ptr ~all"

;;;; MAKE MANUAL ENTRIES BELOW THIS LINE! ;;;;

xx.xxx.135.92 is ns1
xx.xxx.135.91 is ns2
xx.xxx.166.10 is the machine on wich clients are (ispconfig)
all other mail seems to work fine (only this email destination is with problem)

i forgot to mention:
[root@web1 named]# [root@web1 named]# host -t txt destination.tld destination.tld descriptive text "v=spf1 a mx ~all"
[root@web1 named]# host -t txt mail.destination.tld mail.destination.tld descriptive text "v=spf1 a -all"
[root@web1 named]# host -t txt sender.tld sender.tld descriptive text "v=spf1 a mx ptr ~all"



Thank you in advance

[falko]

sender.tld. TXT "v=spf1 a mx ptr ~all"

Did you send from one of the hosts specified in this SPF record?

[sweetz]

yes of course, this is the sender. (client on ispconfig).
he has an email account on that domain.
and that's his SPF settings.
i believe that the ispconfig's default seting for all clients.

[falko]

Can you post the real domain name you sent from so that I can check?

[sweetz]

the sender domail is: mitek.ro

[falko]

I've checked that domain, and everything seems to be fine. I guess it's a misconfiguration on the remote mailserver then...