Ordinarily, when
sendmail builds (rebuilds) an aliases database,
it objects to duplicate
keys on the left of the colon:
staff: bill
staff: leopold 
this is an error
But sometimesfor example, in automatingsuch duplicates
are necessary. In such instances, the -A switch
can be used with the AliasFile
(A) option (see AliasFile) to
cause duplicates to be silently appended:
staff: bill
staff: leopold
... silently modified by sendmail to internally become
staff: bill, leopold
Note that this process is further illustrated in Section 12.4.5.
The -A database switch is useful only with alias
files because those are the only files that
sendmail rebuilds on its own. Beginning with
V8.10, this switch is also useful with the ph type
(ph).
