Overview #
MTA is an acronym for Mail Transfer Agent. Postfix is the MTA used in Mailborder as it is one of the most secure MTA servers available. While very granular and a highly configurable product, the Postfix configuration options in the Master GUI are limited to only a few options that are enough for most administrators. The Postfix configurations on Mailborder servers are built automatically, which provides a consistent and secure environment.
Configuration Options #
The configuration is in the Master GUI here: [ top menu > transport > mail transport settings ]
Maximum Email Size #
The maximum size for any email including all attachments in bytes. Any email exceeding this size will be rejected and will not be quarantined. Default setting: 52428800, which is 50mb.
Internet Protocol #
The internet protocol used by the MTA during SMTP transactions. IPv4, IPv6, or ALL. If IPv6 is not configured for your environment, the option should be set to IPv4. Default setting: ipv4
Reverse DNS Checks #
Check the remote server IP address for DNS mapping. This check is very effective at eliminating connections from nefarious remote servers. None: no checks performed. Basic: check for IP address -> name mapping. Strict: check for IP address -> name mapping, name -> IP address mapping, and verify the name -> IP address matches the remote server IP address. Default setting: basic. Recommended setting: strict.
Cache Cleanup Interval #
The amount of time between address verification database cleanup runs within the MTA measured in hours. Default setting: 6h.
Bounce Queue Lifetime #
Consider a bounce message as undeliverable, when delivery fails with a temporary error, and the time in the queue has reached this limit measured in days. Default setting: 5d
Reject Unverified Recipient #
Reject the request when mail to the RCPT TO address is known to bounce, or when the recipient address destination is not reachable. This is determined by connecting to the destination server with a probe message before accepting any new recipient email. The result is cached for future use. This option can cause the Mailborder server to reject email if the final destination server is unreachable for email verification.
Strict Envelopes #
Require that addresses received in SMTP MAIL FROM and RCPT TO commands are enclosed with <>, and that those addresses do not contain RFC 822 style comments or phrases. This stops mail from poorly written software.
Custom Configuration #
Additional options may be added in the configuration file /etc/mailborder/conf.d/postfix.cf on a limited basis. This file is read during configuration rebuilds. See the file for instructions.
