SMTP/POP3/IMAP port field allows to change default ports of receiving and sending mail messages.

SMTP/POP3/IMAP interfaces field allows to choose server interfaces, through which sending and receiving of mail will happen. By default all interfaces are used.

The following settings are used for applying various restrictions for sending mail.

Maximum message size – creates a restriction for attachments when using web-mail (built-in client roundcube).

Restrict frequent mail sending – turns on restrictions of mail sending through ICS mail server.

Maximum number of messages from one IP per minute – specifies amount of mail, sent per minute, for frequent restriction to turn on. Doesn’t concern messages sent from webmail.

Ignore sending mails from permitted addresses and networks – turns off restrictions for frequent mail sending for addresses and networks from “white list”.

You can set ICS to send outcoming mail through another SMTP-server for all letters, which receivers aren’t local.

For turning on sending outcoming mail through another SMTP-server you should enter its address (domain name or IP) into the “default relay” field and set a port for the connection.

SSL chechbox is used only for SMTPS connection through the port 465. So, for sending letters through 465 port, it must be marked.

When connection is made through 25 port, the checkbox must be unmarked, because otherwise STARTTLS extension will be chosen automatically, depending whether the remote side support this protocol or not.

If you want to send mail through mail.ru / yandex.ru / gmail.com etc SMTP-servers, it’s necessary to use authentication and mark the checkbox “Change sender e-mail”, because for these mail servers it’s vital that sender e-mail matches the user that authenticates in theirs system. The sender address can be put into “Sender email” field.

Permitted networks – networks, that are specified in ICS network interfaces settings. Sending mail from them doesn’t require SMTP authorization, ICS will accept mail from them without checking grey lists, and without checking whether they have valid PTR record.

Addresses, which are allowed forwarding – this is a list of addresses and domains with the same rights as “Permitted networks” have except that you should manually enter this addresses. In this list you can enter domains, mailboxes and IP-addresses.

Addresses which are prohibited forwarding – this is a list of addresses and domains, from which ICS will decline all the mail.

Server name for SMTP – hostname that will be transmitted in SMTP HELO or EHLO commands for remote side when the letter is sent.

Use DLP – initiates start of the service, that checks letters with confidential information prints.

Harddisk for keeping mail – allows to redirect mail store to another hard drive. By default mail is storing on the system partition. When you change the mail store hard drive, all mail will be copied from default partition to the new one. If you already have a sufficient amount of mail, it will therefore take sufficient time. You can monitor this process in the module Maintenance – System - Tasks.

Default authorization domain defines which domain will be added automatically when user authorizes. So, if you specify a domain in this field, users in this domain could authorize without entering the domain.

On creating a mailbox automatically create next folders – contains the list of standard folders that would be created in a mailbox. You can change this list if necessary.

Check mail with Clamav / Dr.Web / Kaspersky antivirus enables checking all income and outcome mail for viruses. If any virus will be founded, instead of a letter user will receive a message about check results, and the original letter will be attached to this message.

Verify DKIM-signature – Enables checking all income to ICS letters whether it has DKIM-signature and whether it’s valid.

Add DKIM-signature – Activates adding a DKIM-signature to letters, that are sent from ICS.

By default, ICS is using the “default” selector. You can have several mail servers for one domain. For every mail server should exist a unique DKIM-selector. If necessary, it can be changed in “Selector” field.

ICS mail server can work either on standard protocol, which does not encrypt data when files are transmitted, or on a secure one.

«Certificate for SMTP» and «Certificate for IMAP/POP3» - enables using encrypted connection with STARTTLS method above using the ordinary TCP connection with SMTP protocol on standard 25 port, or with IMAP/POP3 protocols on standard ports 143/110, respectively, by adding previously created certificate in the field. You can change standard SMTP/POP3/IMAP ports in the related section.

Encryption using STARTTLS extension with SMTP protocol on ICS server is a compromise. If the other side does not support encryption, then the mail will be sent using plain SMTP protocol.

Enable SSL/TLS (SMTPS, IMAPS, POP3S) encryption – enables SMTPS encryption on the port 465, and also IMAPS / POP3S encryption on the ports 993 / 995 respectively. You can change these ports in the related fields.

In ICS mail server only TLSv1, TLSv1.1, TLSv1.2 encryption protocols are used.

Using SSL2 and SSL3 is disabled for better security.