Name
MaxAliasRecursion
Synopsis
When sendmail processes an alias, it essentially
translates one address into new addresses. It must then look up each
new address to see if it, too, is aliased. Clearly, there is a risk
that this process might become recursive or excessively deep. Prior
to V8.10 sendmail, the MAXRCRSN compile-time
macro set the limit on how far this recursion could go. Beginning
with V8.10, the limit is set with this
MaxAliasRecursion
option.
The MaxAliasRecursion
option is declared like this:
O MaxAliasRecursion=num ← configuration file (V8.10 and later) -OMaxAliasRecursion=num ← command line (V8.10 and later) define(`confMAX_ALIAS_RECURSION',`num')← mc configuration (V8.10 and later)
The num
is of type numeric
and, if omitted, becomes zero. If the entire
MaxAliasRecursion
option is omitted, the default
becomes 10. The default for the mc configuration
technique is also 10. If num
is zero or negative,
all aliases will be limited to one transformation, and every one will
cause an error. Whatever the value of num
, when
recursion becomes greater than that number, the following error is
logged and returned as an error in the SMTP dialog, thus bouncing
that address:
554 5.0.0 aliasing/forwarding loop broken (actual aliases deep; num
max)
In general, a value of 10 should be considered the minimum.
The MaxAliasRecursion
option is not safe. If it is
specified from the command line, it can cause
sendmail to give up any special privileges.
Get Sendmail, 3rd Edition now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.