sendmail, 4th Edition

ClientCertFile

File containing the client’s public certificate V8.11 and later

STARTTLS and stream encryption are discussed in detail in STARTTLS on page 202. Among the items you might need to create, or purchase, to set up stream encryption is a certificate for your client side. A client certificate is used by sendmail when it is acting in the role of a sender (dispatching outbound email). It is contained in a file whose location is set with this ClientCertFile option, using declarations that look like this:

O ClientCertFile=path                ← configuration file (V8.11 and later)
-OClientCertFile=path                ← command line (V8.11 and later)
define(`confCLIENT_CERT',`path')     ← mc configuration (V8.11 and later)

Here, path is a full path specification of the file containing the certificate. The path can contain sendmail macros, and if so, those macros will be expanded (their values used) when the configuration file, or command line, is read:

define(`confSERVER_CERT', `${MyCERTPath}/ClntCert.pem')

The path must be a full pathname (must begin with a slash), or the file will be rejected and the following error logged:

STARTTLS: ClientCertFile missing

The path must also live in a directory that is safe (every component of which is writable only by root or the trusted user specified in the TrustedUser option) and must itself be safe (owned by and writable only by root or the trusted user specified in the TrustedUser option; see TrustedUser on page 1112). If it is not, it will be rejected and the following error ...