These sections collect all the advanced settings for the Mail Transport Agent which are not meant to be changed often and for which the default is probably correct.
Warning: change these variables with caution as incorrect values could make your MTA unusable.
System resources
In this section you can adjust the system Resources profile. Please, see the Virtual Machine Hardware Requirements section in the Technical Requirements page.
Note: when hardware resources are changed the appliance will apply a new Resource profile by itself on reboot.
MTA queue lifetime
In this section you can adjust the time for which emails are kept in the outgoing queue.
- Bounce queue lifetime: how long a message stays in the queue before it's considered undeliverable
- Maximal queue lifetime: how long the MTA will retry deferred messages delivery
- Delay warning time: the time after which the sender receives the message headers of email that is still queued
SMTP Banner
In this section you can the SMTP server banner information. This banner is what the sender mailserver sees when it connects to the appliance.
- My hostname: the hostname displayed in the SMTP banner
- MTA Banner: the structure on the banner using the $myhostname and $mail_name variables as placeholder
Recipients features
In this section you can configure recipients related advanced MTA settings.
- Max recipients per message: the maximum number of recipient an email can have
- Plus addressing (subaddressing): the character used to perform a subaddressing operation as the RFC 5233 defines
- Destination concurrency rate: The maximal number of parallel deliveries to the same destination
Denial of Service protection
In this section you can set all the parameters that defines how loaded the MTA can be. Higher values means more MTA load, so more probability of DoS situations. Lower values means less MTA load, so less probability of DoS situations.
- Maximum connections count: the maximal number of connections that a SMTP client may make simultaneously
- Maximum connections rate: the maximal number of connections that a SMTP client may make per minute
- Maximum message rate: the maximal number of message delivery requests that a SMTP client may make per minute
- Maximum recipient rate: the maximal number of recipient addresses that a SMTP client may specify per minute
- Client exceptions: CIDR networks excluded from any DoS limit
HA-Proxy protocol
In this section you can configure a HA-Proxy based load balancing system.
- Enable HA-Proxy protocol: choose to enable or disable the HA-Proxy integration
- Load Balancer IP address: the HA-Proxy load balancing system IP address