Come installare postfix - Invio mail

[Keccogrin90]

Ciao,
vorrei installare postfix per poter inviare le mail in automatico dal terminale di ubuntu.
Seguendo questa guida, ho digitato il comando:

sudo apt-get install postfix

Ed ottengo questo warning seguito da questi errori:

WARNING: The following packages cannot be authenticated!
    postfix
Install these packages without verification? [y/N] y
Err http://us.archive.ubuntu.com/ubuntu/ trusty-updates/main postfix amd64 2.11.0-1ubuntu1
  Could not resolve 'us.archive.ubuntu.com'
E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/p/postfix/postfix_2.11.0-1ubuntu1_amd64.deb  Could not resolve 'us.archive.ubuntu.com'


E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

Grazie in aticipo,
Ciao
P.S. La mia versione di ubuntu è 14.04LTS e la sto usando su macchina virtuale con VMware Workstation 12 Player

[sacarde]

prima hai eseguito: sudo apt-get update ?

[Keccogrin90]

Sì, ho eseguito

sudo apt-get update

E questo è ciò che viene fuori:

Err http://extras.ubuntu.com trusty InRelease
  
Err http://security.ubuntu.com trusty-security InRelease
  
Err http://security.ubuntu.com trusty-security Release.gpg
  Could not resolve 'security.ubuntu.com'
Err http://extras.ubuntu.com trusty Release.gpg
  Could not resolve 'extras.ubuntu.com'
Err http://us.archive.ubuntu.com trusty InRelease
  
Err http://us.archive.ubuntu.com trusty-updates InRelease
  
Err http://us.archive.ubuntu.com trusty-backports InRelease
  
Err http://us.archive.ubuntu.com trusty Release.gpg
  Could not resolve 'us.archive.ubuntu.com'
Err http://us.archive.ubuntu.com trusty-updates Release.gpg
  Could not resolve 'us.archive.ubuntu.com'
Err http://us.archive.ubuntu.com trusty-backports Release.gpg
  Could not resolve 'us.archive.ubuntu.com'
Reading package lists... Done
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty/InRelease  

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-updates/InRelease  

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/InRelease  

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/trusty-security/InRelease  

W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/trusty/InRelease  

W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/trusty/Release.gpg  Could not resolve 'extras.ubuntu.com'

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/trusty-security/Release.gpg  Could not resolve 'security.ubuntu.com'

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty/Release.gpg  Could not resolve 'us.archive.ubuntu.com'

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-updates/Release.gpg  Could not resolve 'us.archive.ubuntu.com'

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/Release.gpg  Could not resolve 'us.archive.ubuntu.com'

W: Some index files failed to download. They have been ignored, or old ones used instead.

[Keccogrin90]

Ho scoperto l'arcano... Non avevo la connessione ad internet