A software programme called an MTA is used to transfer emails from one server to another. This area of the Carbonio Admin Panel, which is divided into sections for Inbound Flow & Security, Outbound Flow, and Antivirus & Antispam, enables configuration of how Carbonio handles and interacts with emails.
Flow Inbound & Security
Optional configurations for incoming email traffic and security checks can be made on this page.
Settings
A custom list of file extensions may be created using the first few parameters to prohibit all attachments. The ADD often restricted EXTENSIONS button on the right-hand side can be used as a shortcut to add many often restricted file extensions. Additionally, any additional file extension may be manually added.
You can use the corresponding option to allow notifications for the administrator and the receiver of the email if an attachment is prohibited.
Rejection
The following scenarios allow for email rejection: when the message seems to have no sender or receiver, or when the sender is not verified. This final option is helpful in preventing remote forged connections to the MTA and unauthenticated email sending.
Checks for Protocols
A few basic checks of the SMTP protocol used by the MTA can be enabled using the third set of options, including those for a client’s IP address and domain, the existence of a FQDN in the address, and HELO greetings when a connection is made.
Outward Flow
The parameters that are applied to messages sent from the local domain are managed on the Outbound Flow page.
General
These choices enable you to set a few parameters that are utilised by the MyNetworks part of the MTA’s configuration, as well as add the client’s IP address and username to the email header and need authentication in order to send emails.
All outgoing email can be forwarded by Relay Host to a server other than Carbonio’s. In the event that the Relay Host cannot be reached, a fallback relay host will be utilised.
Instances
Information on the enabled services on the mail servers set up with the Carbonio installation, including Antispam and Antivirus, Authentication, and DKIM, is displayed at the bottom of the page.
Options under Antivirus & Antispam relate to the Antivirus and Antispam engines.
Antispam
When an email is flagged as spam, its subject can be prefixed with a predetermined string (the most popular being [SPAM] or ***SPAM***), and it can either be rejected (meaning the recipient will never see it) or it can still be delivered.
The two choices on the left-hand side determine whether the email should be instantly destroyed or just tagged as spam. The values for both of the selections (Low, Medium, and High) are proportional to the SpamAssassin spam score, where a score of 20 corresponds to 100% of spam. The default (i.e., the medium setting) tolerance for spam delivery is 33%, whereas the tolerance for spam blocking is 75%. Accordingly, an email with a spam score of 6.6 will be classified as spam, whereas an email with a spam score of 15 will be removed right away. The threshold to flag or remove spam emails will decrease or increase depending on whether the setting is set to Low or High.
You may also examine the outbound traffic and confirm DKIM for further security: If DKIM is enabled for a domain, emails coming from that domain without a DKIM signature are regarded as having been forged and are, thus, invalid.
Definitions of antiviruses
The db.us.clamav.net mirror is the standard one used to retrieve signatures; alternative servers or mirrors can be added by entering their URL in the text box on the left and clicking the ADD button. Selecting existing mirrors and selecting the REMOVE option will erase them.
A file with unique viral signatures can also be manually added or removed by using the textfield on the right side and then clicking the ADD or REMOVE button.
The next setting is the frequency of the mirror’s signature updates, which can range from a few seconds to many weeks.
Queue
This page displays data on the messages managed by the MTA system, sorted by status. The previous update’s timestamp shows, as do two buttons that allow you to RESTART SCAN or manually FLUSH QUEUES.
When you click a server, a dialogue appears with the queue’s content, that is, all the messages organised by status (Queued, Corrupted, Deferred, Incoming, and On Hold). You may also FLUSH QUEUES here.
When you click one of the statuses, a full view of the pending messages emerges. When you choose a message, you may perform the following actions: place it on HOLD; RELEASE, REQUEUE, or DELETE it.