There's no mail error logs but there are mail warnings as below
Dec 25 22:53:26 badbuntu postfix/smtpd: warning: 18.104.22.168: hostname 244-168-245-190.fibertel.com.ar verification failed: Name or service not known
Dec 25 23:59:57 badbuntu postfix/smtpd: warning: 22.214.171.124: address not listed for hostname 16-187-42-89-cable.canals.ro
Dec 26 00:54:41 badbuntu postfix/smtpd: warning: 126.96.36.199: address not listed for hostname localhost
Dec 26 03:54:12 badbuntu postfix/smtpd: warning: 188.8.131.52: hostname cpe-98-145-80-232.natnow.res.rr.com verification failed: Name or service not known
Dec 26 08:18:54 badbuntu postfix/smtpd: warning: 184.108.40.206: address not listed for hostname localhost.
it's odd, when I send an email from another address i get a rejection reply straight away, although often the email does come through but not for about an hour later. A sample mail box is my firstname.lastname@example.org
my name is David!
Should I delete those other name servers from resolv.conf. ? Also my file doesn't end with the question mark like the one you mentioned. I presume this doesn't matter?
Thanks for all your help With this by the way.