Control Relays Controlling which domains can relay mail through Postfix is a very important setting. You certainly will need to relay mail from the domain that Postfix is on. You do not want Postfix to relay mail from other sources, unless they are domains that you control as you will end up begin an open relay for spammers. How to Control Relays Postfix will not allow the server to be an open relay by default. Several parameters control who can use ...

Maps are the files and databases created from files that are used to look up information. The basic structure of maps are two columns, a left-hand side (key) and a right-hand side (value). key value Postfix uses a number of map types. These maps are critical to Postfix looking up information quickly. To view the supported map types on your system use this command: # postconf ...

Lookup Tables are simple tables that allow Postfix to access configuration information that it needs. An example is when an organization would like to rewrite the email addresses so that they look different to outside clients. The parameter canonical_maps is the file that is used to make these changes and is used as a Lookup Table. In the example the organization wants to change the tsmith@example.org to tom.smith@example.org outside of the network. The ...

Managing Mail Limits The main.cf file contains several settings to manage mail limits. Limit Recipients This parameter limits the number of recipients for a single message. The default is 1000 set in the smtpd_recipient_limit setting. Message Size Limit The message size is restricted to 10 MB by default. This is a setting that you will need to consider disk space and the needs of users. This is set in the message_size_limit parameter. ...