Postfix and Dovecot: Not delivering external mails

Hi, I followed this guide https://library.linode.com/email/postfi … 0.19-mysql">https://library.linode.com/email/postfix/postfix2.9.6-dovecot2.0.19-mysql

When I send a mail from my accounts (@mydomain.com) all works fine (the mail is sent correctly to another external like gmail or internal account).

The problem is when I send a mail from external accounts to one of my internal accounts, the mail is never delivered.

Only is delivered if I send from one of my accounts to another. In that case I can see the next lines in dovecot log:

Dec 19 16:24:54 lmtp(15235, info@copprobicba.com.ar): Info: 6T4jLQZIs1KDOwAAL1wRtg: msgid=<bf20b53be7e56677af62b7838d1e52f3@copprobicba.com.ar>: saved mail to INBOX</bf20b53be7e56677af62b7838d1e52f3@copprobicba.com.ar> 

And in postfix log:

Dec 19 16:29:54 copprobi-server postfix/lmtp[15326]: B3589255A0: to=<info@copprobicba.com.ar>, relay=copprobicba.com.ar[private/dovecot-lmtp], delay=3407, delays=3407/0.06/0.02/0.03, dsn=2.0.0, status=sent (250 2.0.0 <info@copprobicba.com.ar>r9IkLjJJs1LfOwAAL1wRtg Saved)</info@copprobicba.com.ar></info@copprobicba.com.ar> 

But in the other case (external account to mydomain account) Postfix receives and process the mail, but never delivers the mail to lmtp. The line starting with "postfix/lmtp" does never appears in this case.

Can anybody help me please?

Thanks!