Consider the following:
----- Transcript of session follows -----
>>> RCPT To:
<<< 550 cannot open /tmp/.../getshell: No such file or directory
550 5.7.1 cannot open /tmp/.../getshell: No such file or directory
This bounced mail message indicates that someone tried to become root by breaking
through your aliases database.
Users are added to the list of those who get copies of bounced messages with the
PostmasterCopy option:
O PostmasterCopy=postmaster,securitymaster
?†‘
added
Here, securitymaster (probably an alias to a real user) was added.
4.8.2.7 The PrivacyOptions option
The PrivacyOptions option (?§24.9.86 on page 1065) is used to limit the amount of
information offered to the outside world and to limit other kinds of access. The most
restrictive setting for the PrivacyOptions option is probably best:
define(`confPRIVACY_FLAGS??, ``goaway,restrictmailq,restrictqrun????)
This setting disables the EXPN and VRFY SMTP commands, requires other sites to
identify themselves before sending mail, and limits access to the mail queue directory.
As a side effect, it also disables DSN parameters because goaway includes
noreceipts. If that is a problem for you, you can manually set up everything that
goaway does, but exclude noreceipts.* Note that the following line is split to fit the
page:
define(`confPRIVACY_FLAGS??, ``needmailhelo,noexpn,novrfy,noverb,authwarnings,
restrictmailq,restrictqrun????)
As a general rule, it is best to begin with tight security.
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