Module ngx_mail_smtp_module

Directives
smtp_auth
smtp_capabilities
smtp_client_buffer
smtp_greeting_delay

Directives

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

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

login
AUTH LOGIN
plain
AUTH PLAIN
cram-md5
AUTH CRAM-MD5 . In order for this method to work, the password must be stored unencrypted.
external
AUTH EXTERNAL (1.11.6).
none
Authentication is not required.

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 the authentication, when nginx transparently proxies the client connection to the backend).

The current list of standardized extensions is published at www.iana.org .

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 a platform.

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.