Create bridges between virtual network cards

Each added virtual network interface use it's own scope to communicate outside the server.
When using Postfix multiple instance, you need to create bridges between virtual network interfaces add the physical network interface in order to allow communicate outside the server.

This prevents errors from Postfix virtual instances like:

smtp[2960]: connect to mx2.rog.mail.yahoo.com[98.139.214.154]:25: Connection timed out

  • Click on the Network icon on the top top icon list.
  • Choose "bridges" tab.
  • Click on "New rule"
  • To allow outgoing connection from the virtual address to Internet, choose the Virtual Interface Card on the left and link to the physical Network interface to the right.
  • Click on Add the bridge button

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Howto test ?

you can logon on the system console and use nc to try to communicate with a specific interface:

nc -s 192.168.20.141 98.139.214.154 25

Means: Use the 192.168.20.141 interface and open a session on the yahoo mail server 98.139.214.154 on port 25