STMP Out

The Protocols page lets system administrators configure settings for message sent out from a SmarterMail server.

Use this card to specify the following outgoing SMTP settings:

Options

Outbound IPv4 - The IPv4 address used to connect to external SMTP servers when a message is sent by the domain. If multiple IPv4 IPs are on the server, they will be listed in the dropdown along with the following:

Use Primary IP on NIC - This will use the IP address that's assigned to the Network Interface Card (NIC) on the SmarterMail server.
Use the Domain's IP - When a domain is set up by a system administrator, they can assign a specific IP address from the server as the "Outbound IPv4" address for that domain.
Rotate IP List - Allows system administrators to select a number of different IP addresses that will be used, and the order in which they'll be used, to send email should connection failures or time-outs occur.
Disable - This disables the use of IPv4 on the server.

Outbound IPv6 - The IPv6 address used to connect to external SMTP servers when a message is sent by the domain. If multiple IPv6 IPs are on the server, they will be listed in the dropdown along with the following:

Use Primary IP on NIC - This will use the IP address that's assigned to the Network Interface Card (NIC) on the SmarterMail server.
Use the Domain's IP - When a domain is set up by a system administrator, they can assign a specific IP address from the server as the "Outbound IPv6" address for that domain.
Rotate IP List - Allows system administrators to select a number of different IP addresses that will be used, and the order in which they'll be used, to send email should connection failures or time-outs occur.
Disable - This disables the use of IPv6 on the server.

Enable DNS Caching - Enable this setting to cache the results of DNS calls in SmarterMail. When enabled, all DNS query results are stored for a period of time determined in the configuration (time-to-live) of domain name records. This decreases the query load placed on the authoritative servers and ensures that answers to these queries are stored locally for rapid querying, thereby speeding up the delivery of messages.
Append X-Smartermail-Authenticated-As Header - Toggling the slider to the right means that outgoing messages will have a new line item in the message header called "x-smartermail-authenticated-as" that demonstrates that the message sender was verified using SMTP authentication. This header can then be used by antispam services for validation.
Disable Remote Bounces - This setting disables bounce messages for messages that fail to reach remote recipients. That means that when a SmarterMail user emails an external recipient (any user not on their domain) and their email fails to deliver, they will NOT receive a bounce message from the recipient's server. Note: This setting disables bounce messages for remote/external deliveries only. A SmarterMail user who sends an email to a user on the same domain will still receive a bounce message if that local delivery fails.
Enforce strict certificate validation - This setting prevents the server from connecting to servers over SSL/TLS that have an invalid certificate For example, this prevents SSL/TLS connections to servers with out-of-date certs or domain name mismatches on their certificate.

Note: Disabling this is not recommended because it may allow a third party to setup a rogue certificate and intercept communications.

Relaxed certificate name validation - Dependent on the enforcement of strict certificate validation, when this setting is enabled, communciation with domains that have expired certificates, self-signed certificates, or other certificates with certifying authority issues will continue to be rejected. However, issues with certificate naming will be ignored as long as the root top level domain is on the certificate. For example, when using a wildcard certificate issued for "*.domain.com", communication with domains such as "mail.domain.com", "www.mail.domain.com", "www.mail17.email.domain.com", etc. would all be allowed as long as the root certificate was NOT expired and was issued for "domain.com".

Delivery Settings

Command Timeout (Seconds) - If the server receives a command that sends large amounts of data but the data stops coming in for this number of seconds, the command will be aborted. By default, the command times out after 60 seconds.
Max Delivery Threads - The maximum number of messages that can be sent at one time to email addresses that are not on the local server. If a message cannot be sent, the SmarterMail server's multi-threading capabilities will move on to the next message and eventually get back to the one it skipped. This action can save tremendous amounts of time when compared to some other mail servers that stall the spool if a message cannot be sent right away. By default, the max delivery threads is 50.
Max Recipients Per SMTP Session - The maximum number of recipients that can be included in one SMTP session. For example, with the limit set to the default of 500, an email containing 600 recipients would utilize two SMTP sessions for delivery - one with 500 recipients and the other with 100. This setting can useful if a receiving server rejects sessions that exceed their allotted recipient limit.

Note: Setting this limit to Unlimited is not recommended unless there is a specific case for doing so.

IP Rotation Settings

This card only appears if Rotate IP List is selected for either Outbound IPv4 or Outbound IPv6. The following settings are available:

IP Rotation Type - How SmarterMail will rotate the IPs.

Delivery Count - IPs will be rotated based on the number of deliveries made by individual IP addresses.

Deliveries per IP - The number of messages sent using a particular IP before the IP is rotated

Time - IPs will be rotated based on the number of minutes a particular IP has been active in SmarterMail.

Minutes per IP - The number of minutes a particular IP has been in service before it is rotated.

Enable Failure Tracking - When toggled on, SmarterMail will begin the IP rotation process based on the number of failures specified.

Failure Count in Window - The number of failures that occur within the Failure Time Window. Once this number is reached within the window, the IP rotation will occur.
Failure Time Window (Minutes) - The time window used for measuring the Failure Count in Window.
Failure Time Skip (Minutes) - The number of minutes before an IP that was skipped due to failures will be re-used in the IP rotation.

Enable RBL Tracking When toggled on, SmarterMail will begin the IP rotation process based on whether an IP is listed by one of the RBLs listed on the RBL Providers tab.

RBL Check Interval (Minutes) - The amount of time between when the IP address is checked against a specific RBL.
RBL Skip Duration (Minues) - The number of minutes before an IP that was listed by and RBL will be re-used in the IP rotation.

Use Primary IP if all other IPs are unavailable - Enable this setting to have SmarterMail automatically fall back to the primary IP when a failure has occurred. SmarterMail will only attempt to connect once if this option is enabled.

IPv4 Addresses

This tab is used for adding IPs that will be used when Rotate IP List is enabled for Outbound IPv4. To select an IP for this list, click the New button. When you do, the Add IP Address modal will appear:

IP Address - This dropdown lists all IP addresses available on the server. To add an IP address for rotation, select it from the dropdown and then click the Add button. IPs can be removed from this list by selecting the IP address and then clicking the Delete button

IPv6 Addresses

This tab is used for adding IPs that will be used when Rotate IP List is enabled for Outbound IPv6. To select an IP for this list, click the New button. When you do, the Add IP Address modal will appear:

IP Address - This dropdown lists all IP addresses available on the server. To add an IP address for rotation, select it from the dropdown and then click the Add button. IPs can be removed from this list by selecting the IP address and then clicking the Delete button

RBL Providers

This tab is used for adding RBLs that will be used when Enable RBL Tracking is enabled for IP Rotation Settings.

Hostname - The hostname of the RBL to use. (E.g., BRBL)
Required Lookup Values - The required lookup value for an RBL is typically a specific IP address within the 127.0.0.0/8 range, which is used to indicate the reason for the listing. For example, the Barracuda Reputation Block List (BRBL) requires a lookup value of 127.0.0.2 to trigger a spam score. Similarly, Spamhaus's Zen blocklist uses 127.0.0.2 for spam-related listings. The exact value can vary between RBL providers, and the meaning of the returned IP address is defined by the specific RBL's documentation.