Other questions on amavis.conf

[Robert Moskowitz]

Use of single and double quotes around values:

Is there some meaning to when single and double quotes are used?  Or is 
it to avoid possible substitutions to use single instead of double quotes?

For example:

$mydomain = 'test.htt-consult.com';   # a convenient default for other 
settings

Why is a single quote used here?  I would venture that no special reason 
other than 'because', and I can change it to a double quote.


Is there a way for @mynetworks to read in an external file that would be 
easier to maintain (like I do with acls in dns) rather than needing to 
work with this value in amavis.conf.  And if so, what would be the 
structure of content in that file?

thanks