SMTP

Adds SMTP support to the mail proxy: Angie handles an SMTP client itself until the authentication server accepts the client, then relays the session to a backend. Until then, Angie answers HELO and EHLO and receives the client's credentials by one of the methods listed under smtp_auth (see How It Works).

When building from the source code, the module is built by default together with the Mail module (enabled with --with-mail); it can be disabled with the build option --without-mail_smtp_module.

In packages and images from our repositories, the module is included in the build.

Directives

smtp_auth

Syntax	smtp_auth method ...;
Default	smtp_auth plain login;
Context	mail, server

Sets permitted methods of SASL authentication for SMTP clients. Supported methods are:

plain	AUTH PLAIN
login	AUTH LOGIN
cram-md5	AUTH CRAM-MD5. In order for this method to work, the password must be stored unencrypted.
external	AUTH EXTERNAL
xoauth2	AUTH XOAUTH2
oauthbearer	AUTH OAUTHBEARER
none	Authentication is not required. Angie still queries the authentication server, after the client's RCPT TO command, to choose the backend (see How It Works).

Plain text authentication methods (AUTH PLAIN and AUTH LOGIN) are always enabled, though if the plain and login methods are not specified, AUTH PLAIN and AUTH LOGIN will not be automatically included in smtp_capabilities.

smtp_capabilities

Syntax	smtp_capabilities extension ...;
Default	—
Context	mail, server

Sets the SMTP protocol extensions list that is passed to the client in response to the EHLO command. The authentication methods specified in the smtp_auth directive and STARTTLS are automatically added to this list depending on the starttls directive value.

It makes sense to specify the extensions supported by the MTA to which the clients are proxied (if these extensions are related to commands used after authentication, when Angie transparently proxies the client connection to the backend).

smtp_client_buffer

Syntax	smtp_client_buffer size;
Default	smtp_client_buffer 4k|8k;
Context	mail, server

Sets the size of the buffer used for reading SMTP commands. By default, the buffer size is equal to one memory page. This is either 4K or 8K, depending on the platform.

smtp_greeting_delay

Syntax	smtp_greeting_delay time;
Default	smtp_greeting_delay 0;
Context	mail, server

Allows setting a delay before sending an SMTP greeting in order to reject clients who fail to wait for the greeting before sending SMTP commands.