121 lines
4 KiB
Prolog
121 lines
4 KiB
Prolog
<!doctype html public "-//W3C//DTD HTML 4.01 Transitional//EN"
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"https://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<title>Postfix Configuration Parameters </title>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link rel='stylesheet' type='text/css' href='postfix-doc.css'>
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}
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</script>
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</head>
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<body>
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<h1><img src="postfix-logo.jpg" width="203" height="98" alt="">Postfix Configuration Parameters </h1>
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<hr>
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<h2> Postfix main.cf file format </h2>
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<p> The Postfix main.cf configuration file specifies a very small
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subset of all the parameters that control the operation of the
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Postfix mail system. Parameters not explicitly specified are left
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at their default values. </p>
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<p> The general format of the main.cf file is as follows: </p>
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<ul>
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<li> <p> Each logical line is in the form "parameter = value".
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Whitespace around the "=" is ignored, as is whitespace at the end
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of a logical line. </p>
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<li> <p> Empty lines and whitespace-only lines are ignored, as are
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lines whose first non-whitespace character is a `#'. </p>
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<li> <p> A logical line starts with non-whitespace text. A line
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that starts with whitespace continues a logical line. </p>
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<li> <p> A parameter value may refer to other parameters. </p>
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<ul>
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<li> <p> The expressions "$name" and "${name}" are recursively
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replaced with the value of the named parameter. The parameter name
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must contain only characters from the set [a-zA-Z0-9_].
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An undefined parameter value is replaced with the empty value. </p>
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<li> <p> The expressions "${name?value}" and "${name?{value}}" are
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replaced with "value" when "$name" is non-empty. The parameter name
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must contain only characters from the set [a-zA-Z0-9_]. These forms are
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supported with Postfix versions ≥ 2.2 and ≥ 3.0, respectively.
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</p>
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<li> <p> The expressions "${name:value}" and "${name:{value}}" are
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replaced with "value" when "$name" is empty. The parameter name must
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contain only characters from the set [a-zA-Z0-9_]. These forms are
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supported with Postfix versions ≥ 2.2 and ≥ 3.0, respectively.
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</p>
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<li> <p> The expression "${name?{value1}:{value2}}" is replaced
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with "value1" when "$name" is non-empty, and with "value2" when
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"$name" is empty. The "{}" is required for "value1", optional for
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"value2". The parameter name must contain only characters from the
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set [a-zA-Z0-9_]. This form is supported with Postfix versions
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≥ 3.0. </p>
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<li> <p> The first item inside "${...}" may be a relational expression
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of the form: "{value3} == {value4}". Besides the "==" (equality)
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operator Postfix supports "!=" (inequality), "<", "≤", "≥",
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and ">". The comparison is numerical when both operands are all
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digits, otherwise the comparison is lexicographical. These forms
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are supported with Postfix versions ≥ 3.0. </p>
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<li> <p> Each "value" is subject to recursive named parameter and
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relational expression evaluation, except where noted. </p>
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<li> <p> Whitespace before or after each "{value}" is ignored. </p>
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<li> <p> Specify "$$" to produce a single "$" character. </p>
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<li> <p> The legacy form "$(...)" is equivalent to the preferred
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form "${...}". </p>
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</ul>
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<li> <p> When the same parameter is defined multiple times, only
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the last instance is remembered. </p>
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<li> <p> Otherwise, the order of main.cf parameter definitions does
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not matter. </p>
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</ul>
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<p> The remainder of this document is a description of all Postfix
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configuration parameters. Default values are shown after the
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parameter name in parentheses, and can be looked up with the
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"<b>postconf -d</b>" command. </p>
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<p> Note: this is not an invitation to make changes to Postfix
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configuration parameters. Unnecessary changes are likely to impair
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the operation of the mail system. </p>
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<dl>
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