By default, Plesk works in cooperation with mail server software, which provides email services for mailboxes and mailing lists. After installation, the mail server is configured automatically and is ready to serve. However, we recommend that you review the default settings to make sure that they satisfy your needs.

To view or configure the mail service settings:

Go to Tools & Settings > Mail Server Settings (in the Mail group).

General

1. Leave the Enable mail management functions in Plesk checkbox selected if you want to allow your users to create mail accounts through Customer Panel and use the mail services provided by the Plesk-managed mail server. If you are using an external mail server, clear this checkbox.

2. You can change the Installed mail server and Installed IMAP/POP3 server by using the corresponding links that lead to the Plesk Installer GUI page.

3. If you want to limit the size of an email message that can be sent through your server, type the required value in kilobytes into the Maximum message size box. Otherwise, leave this field blank.

4. In Plesk for Linux, you can change the default mail server limits on the number of concurrent connections that mail users can make to the server. This is useful, for example, for mail hosters who need to increase the number of concurrent connections to the mail server.

   Also, you can change the limit on the number of connections from the same IP address. A low limit impacts users who connects to the mail server from multiple computers from behind a firewall, as well as users who have more than one mail account.

   Note that to set up adequate numbers, you should estimate not only the possible total number of connections, but also the memory and CPU resources of the server.

   The total number of connections is counted as a sum of all connections made via the same protocol(IMAP, POP3, IMAP over SSL/TLS, or POP3 over SSL/TLS), so a single limit works for any of the protocols.

   If you use Courier IMAP, you can specify the following limits:

   • Maximum number of connections (IMAP, POP3, IMAP over SSL/TLS, or POP3 over SSL/TLS). This represents the maximum number of IMAP or POP3 processes that can be started on the server.
   • Maximum number of connections per IP address. This represents the maximum number of connections via the same protocol that the server will accept from the same IP address.

   These settings correspond to the Courier IMAP configuration parameters MAXDAEMONS and MAXPERIP.

   If you use Dovecot, you can specify the following limits:

   • Maximum number of connections (IMAP, POP3, IMAP over SSL/TLS, or POP3 over SSL/TLS).This represents the maximum number of mail users that can be logged in at the same time.
   • Maximum number of connections for a user per IP address. This represents the maximum number of connections via the same protocol that a mail user can establish from one IP address.

   These settings correspond to the Dovecot configuration parameters process_limit and mail_max_userip_connections.

5. (Optional) To allow your customers to send email messages through port 587, select the “Enable SMTP service on port 587 on all IP addresses” checkbox (Plesk for Linux) or “Switch on message submission on all IP addresses” (Plesk for Windows) and allow connections on port 587 in your firewall settings.

   You may also ask your customers to specify the port 587 for outgoing SMTP connections in their email programs’ settings.

6. In Plesk for Linux with the Postfix mail server, you can change the IP address used for sending mail. Also, if your server sends mail from domain IP addresses, you can specify which name will be used as the host name in SMTP greetings.

   Choose from the three options:

   • Send from domain IP addresses. By default, mail from each domain is sent from the domain’s IP address. The host name used in the SMTP greeting is the Plesk server host name specified in Tools&Settings > Server Settings. Selecting this option may result in mail sent from some or all domains being marked as spam if the Plesk server host name fails to resolve properly, or if the domain’s IP is different from the one to which the Plesk server host name resolves.

     This option works best if you have a single IP address on the Plesk server.

   • Send from domain IP addresses and use domain names in SMTP greeting. If selected, Plesk changes the mail server configuration so that the SMTP greeting contains the name of the domain from which the email message is sent.

In addition, selecting this option on Plesk servers hosting a large (more than 100) number of domains will likely result in significantly increased server load.

This option works best if you have allocated a dedicated IP address to every domain hosted on the Plesk server, and the number of domains hosted on the server is not very large.

• Send from the specified IP address. You might want to use certain IPv4 and IPv6 addresses for all outgoing mail. Sending all mail from the specified address might be useful, for example, if the IP address of the mail server was added to a public black list, such as the Spamhaus or OpenBL lists. If you select None, outgoing mail will not be sent.

Relay Options

Select the mail relay mode.

With closed relay the mail server will accept only the messages addressed to the users who have mailboxes on this server. Your customers will not be able to send any mail through your outgoing SMTP server, therefore, we do not recommend closing mail relay.

With relay after authorization, only your customers will be able to receive and send email through your mail server. We recommend that you leave the authorization is required option selected, and select authentication methods:

• POP3 lock time. With POP3 authorization, once users have successfully authenticated to the POP server, they are permitted to receive and send email through the mail server for the specified period of time.
• SMTP. With SMTP authorization, your mail server requires authorization if the email message must be sent to an external address.

There is also an option to allow open relay without authorization, which, by default, is hidden from the user interface. Opening mail relay without authorization is not recommended because it allows spammers to send unsolicited mail through your server. If you want to set the open relay, log in to the server’s file system, locate the file root.controls.lock in your Plesk installation directory (PRODUCT_ROOT_D/var/root.controls.lock on Linux and PRODUCT_DATA_D/var/root.controls.lock on Windows platforms) and remove the line /server/mail.php3:relay_open from this file. The open relay option will appear in your control panel.

In Plesk for Windows, if you do not wish to use relay restrictions for networks that you trust, specify the network IP and mask in the Use no relay restrictions for the following networks field (for example, 123.123.123.123/16) and click the icon. To remove a network from the list, click the icon corresponding to the network you wish to remove.

The relay hosts on the networks in the list are considered not to be potentially operated by spammers, open relays, or open proxies. A trusted host could conceivably relay spam, but will not originate it, and will not forge header data. DNS blacklist checks will never query for hosts on these networks.

SmarterMail mail server allows you to switch on the Require SMTP Authentication option on the domain level. However, this option can be switched on only when open relay is selected on the server level in Plesk. With other relay modes, Plesk switches off this option. To switch on this option, allow open relay in Plesk as described above and go to SmarterMail > Settings > Defaults > Domain Defaults.

Limitations on Outgoing Email Messages

Switch on limitations on outgoing email messages. This option is used to prevent sending spam email messages from the Plesk server. For details, see Protection from Outbound Spam.

Besides the limits, you can adjust the following settings:

• Allow scripts and users to use Sendmail (Linux only). Scripts and system users of subscriptions will be able to send email messages by using Sendmail even if the limits for a mailbox and domain are exceeded. The maximum number of messages that can be sent will be defined by the limit for a corresponding entire subscription. Messages are sent on behalf of the subscription’s system user.

• Show reports based on statistics for the last (specify the period of time). If there is an attempt to exceed the limits on outgoing mail during that period, the Plesk Home page displays an alert. Also, reports are created based on the statistics for this period by default.

• Send an email notification every (specify the period of time). If there is an attempt to exceed the limits on outgoing mail during that period, the administrator receives an email notification.

  If you switch on limitations on outgoing email messages, a new link, Outgoing Mail Control link (in the Mail group of Tools & Settings) appears. Use this link to see detailed statistics on outgoing email messages for all Plesk objects.

Before configuring the limitations on outgoing mail on Windows hosting, do the following:

1. Close the open relay and remove all addresses from the relay’s list of trusted networks and IP addresses.
2. In Tools & Settings > External SMTP Server make sure that the option Allow Plesk to send email notifications through this SMTP server is switched on.

Antivirus Settings

Select the antivirus program that should be used on the server. For details, see Antivirus Software.

Spam Protection

Select the spam protection options that should be used on the server. If you wish to set up spam protection systems, such as SpamAssassin spam filter, or protection systems based on DKIM, DNS Blackhole Lists or Sender Policy Framework (SPF), proceed to the section Antispam Tools.

Names for POP3/IMAP Mail Accounts

If you are using the Qmail mail server, you can select the mail account format.

Selecting the Use of short and full names is allowed option will allow users to log in to their mail accounts by specifying only the left part of email address before the @ sign (for example, username), or by specifying the full email address (for example, username@your-domain.com).

To avoid possible authorization problems for email users who reside in different domains but have identical user names and passwords, we highly recommend that you choose the Only use of full mail account names is allowed option.

Once you have set your mail server to support only full mail account names, you will not be able to switch back to supporting short account names until you make sure there are no encrypted passwords for mailboxes and user accounts with coinciding user names and passwords residing in different domains.