Using POP¶

msgchk will normally check all the local mail drops, but if the option “pophost:” is set in the mts configuration file “mts.conf”, or if the -host hostname switch is given, msgchk will query this POP service host as to the status of mail waiting. The -port switch specifies the port name or number used to connect to the POP server. If unspecified, the default is “pop3”.

To specify a username for authentication with the POP server, use the -user username switch. The credentials profile entry in mh-profile(5) describes the ways to supply a username and password.

For debugging purposes, there is also a switch -snoop, which will allow you to watch the POP transaction take place between you and the POP server. If -sasl -saslmech xoauth2 is used, the HTTP transaction is also shown.

If nmh has been compiled with SASL support, the -sasl switch will enable the use of SASL authentication. Depending on the SASL mechanism used, this may require an additional password prompt from the user (but the netrc file can be used to store this password, as described in mh-profile(5). The -saslmech switch can be used to select a particular SASL mechanism.

If SASL authentication is successful, msgchk will attempt to negotiate a security layer for session encryption. Encrypted traffic is labelled with `(encrypted)' and `(decrypted)' when viewing the POP transaction with the -snoop switch; see post(8)'s description of -snoop for its other features.

If nmh has been compiled with OAuth support, the -sasl -saslmech xoauth2 switch will enable OAuth authentication. The -user switch must be used, and the user-name must be an email address the user has for the service, which must be specified with the -authservice service switch. Before using this, the user must authorize nmh by running mhlogin and grant authorization to that account. See mhlogin(1) for more details.

If nmh has been compiled with TLS support, the -tls and -initialtls switches will require the negotiation of TLS when connecting to the remote POP server. The -tls switch will negotiate TLS as part of the normal POP protocol using the STLS command. The -initialtls switch will negotiate TLS immediately after the connection has taken place, before any POP commands are sent or received. Data encrypted by TLS is labeled `(tls-encrypted)' and `(tls-decrypted)' with viewing the POP transaction with the -snoop switch. The -notls switch will disable all attempts to negotiate TLS.

When using TLS the default is to verify the remote certificate and SubjectName against the local trusted certificate store. This can be controlled by the -certverify and -nocertverify switches. See your OpenSSL documentation for more information on certificate verification.