Plesk Server-Wide Mail Settings

Configuring server-wide mail settings in Plesk

Do you know if your Plesk mail server is configured correctly for you? Well, let us help. We’re here to show you how you can configure Plesk server-wide mail settings. So that they can best suit your business needs.

Reliable email infrastructure is a must for any business industry. You need an email server to send and receive emails. In many cases, Web and mail servers are combined into one machine. Plesk Obsidian also supports mail server software in this way, except you don’t need to set it up before you get started. Because we’ve already done that for you.

But it’s worth taking a look at your settings to make sure that Plesk mail server is configured in a way that will best suit your needs. So, follow these step-by-step instructions, and get your email configuration working exactly how you want it.

Plesk server configuration mail settings

Plesk server configuration mail settings

To do this: Go to Tools & Settings > Mail Server Settings (in the Mail group).


  1. Look at the Enable mail management functions in the Plesk checkbox. If it’s already ticked, then don’t touch it. Since this lets users create email accounts and use services while in the Customer Panel. But if you want to use an external mail server, make sure the box remains unticked.
  2. Easily change the Installed mail server and Installed IMAP/POP3 server by clicking the appropriate links to take you to the Plesk Installer GUI page.
  3. The Maximum message size box does what you expect. You can specify sizes or leave it empty.
  4. If using Plesk mail for Linux. Set how many simultaneous connections mail users can make to the server. Because this is handy if you require more connections.
  5. You can also vary the total number of connections from the same IP address. Setting a lower max. affects any users behind a firewall who connect via multiple computers. Moreover, it also affects others who have multiple mail accounts.

Offering the right resources isn’t just about how many connections are available at the same time. It’s also about how much CPU power and disk space you should make available.

You can calculate total connections by adding up all the ones which share the same protocol (IMAP, POP3, IMAP over SSL/TLS, or POP3 over SSL/TLS). A single limit may work for any of these.

Plesk mail server settings for Courier IMAP users

If you’re a Courier IMAP user, you can set these limits in your Plesk mail server settings:

    • Maximum number of connections (IMAP, POP3, IMAP over SSL/TLS, or POP3 over SSL/TLS). This shows the total IMAP or POP3 processes you can start on the server.
    • Maximum number of connections per IP address.
      Here you can see the max. possible connections using identical protocols, which the server accepts from any given IP address.

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

Plesk mail server settings for Dovecot users

If you use Dovecot, you can use these limits:

    • Maximum number of connections (IMAP, POP3, IMAP over SSL/TLS, or POP3 over SSL/TLS).
      This is the max amount of mail users that can log in simultaneously.
    • Maximum number of connections for a user per IP address.
      This is the max. number of connections using the same protocol that a mail user can establish from a single IP address.

These settings relate to the Dovecot configuration parameters process_limit and mail_max_user ip_connections.

  1. (Optional) To email using port 587 ( read more about Plesk ports ).Choose the “Enable SMTP service on port 587 on all IP addresses” tickbox (Plesk for Linux) or“Switch on message submission on all IP addresses” (Plesk for Windows) and permit connections for port 587 in your firewall settings.

You can also select Port 587 for outward-bound SMTP connections from your email program settings.

Changing IP on Postfix server (Plesk for Linux)

In Plesk for Linux on a Postfix mail server, you can alter the mail IP address. And if your server sends mail from domain IP addresses, you can decide which name you prefer to be used as the host name in SMTP greetings.

Select one of these three options:

    • Send from domain IP addresses.
      Mail from each domain is sent from the domain’s IP address by default. The host name in the SMTP greeting is the Plesk server host name. You can see this in Tools and Settings > Server Settings. Note – if you choose this option, mail from some or all domains may go into spam. This happens if the Plesk server host name doesn’t resolve correctly. Or if the domain’s IP is different from the one the Plesk server host name resolves.

This option is most effective if you have one IP address on the Plesk server.

    • Send from domain IP addresses and use domain names in SMTP greeting.
      If you select this, Plesk alters the mail server configuration. So that the SMTP greeting contains the name of the domain from which the email message is sent.

Warning: If you select this option then mail sent from some or all domains may be marked as spam. This happens if the destination mail server uses cbl, and more than one domain on the Plesk server uses the same IP address.

If you select this option on Plesk servers hosting 100 domains or more, you’ll probably create a much greater server load.

This option is most effective if every domain hosted on the Plesk server has a dedicated IP address. And if the server only hosts a small number of domains:

  • Send from the specified IP address.
    You may want to use particular IPv4 and IPv6 addresses for all outgoing mail. It can be useful to send every email from the specified address. Like when you add the mail server’s IP address to a public black list, such as the OpenBL or Spamhaus lists. If you choose to select None, outgoing mail won’t be sent.

Plesk mail settings – relay options

Choose mail relay mode. If you’re in closed relay mode, your mail server can only support messages addressed to users with mailboxes on the server. It’s best to leave mail relay open. Otherwise customers won’t be able to send mail using your outgoing SMTP server.

If you select relay after authorization, you’ll only see customer emails through your mail server. We advise you to leave the authorization is required option unchanged. Then choose your authentication methods:

  • POP3 lock time:Once you succeed in authenticating the POP server using POP3 authorization. You may exchange emails through the mail server for the permitted amount of time.
  • SMTP: SMTP authorization requires all externally-bound emails to be authorized.

Note – It can be dangerous to open mail relay without authorization. Because it means that spammers can send unsolicited mail through your server. You can do this if you want to. But, the option is hidden by default. So you’ll have to go out of your way to do it.

To set the open relay
Log in to the server’s file system.
Find 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)

Then take this line -/server/mail.php3:relay_open from this file. You should now see the open relay option control panel.

Plesk relay options for Windows users

Follow these instructions if you’re using Plesk for Windows. And you don’t want to use relay restrictions for trusted networks.

  1. Specify the network IP.
  2. Mask in the Use no relay restrictions for the following networks field (for example,
  3. Click the icon that indicates the network you’d like to remove

Any relay hosts on the list of networks are there because they’re not thought to be run by spammers, open relays, or open proxies. A trusted host can potentially relay spam, but won’t originate it, or forge header data. DNS blacklist checks won’t ever query for hosts on these networks.

SmarterMail mail server

A SmarterMail mail server lets you switch on the Require SMTP Authentication option on the domain level. You can only turn this option on when you select open relay on the server level in Plesk.

With other relay modes, Plesk turns this option off. To turn this option on, allow open relay in Plesk – as described above – then go to SmarterMail > Settings > Defaults > Domain Defaults.

Plesk mail server configuration to limit outgoing email messages

Plesk mail server configuration to limit outgoing email messages

Turn on limitations on outgoing email messages. This option stops spam being sent from the Plesk server. See Protection from Outbound Spam for details.

Note: Limits in server-wide mail settings are default values from service plans and subscriptions. You can set your own limits. More info on this is available in How Limits Work.

Besides limits, you can also alter these settings:

  • Send an email notification every (choose how often).
    The administrator gets an email notification whenever the limit is exceeded.
  • Allow scripts and users to use Sendmail (Linux only).
    This lets scripts and subscription system users to send emails using Sendmail – even if the limits for a mailbox and domain are exceeded. You can determine the highest allowed number of sent messages by setting the limit for a corresponding entire subscription. You can send messages on behalf of the subscription’s system user.
  • Show reports based on statistics for the last (specify time period).
    If someone attempts to exceed the limits on outgoing mail during that time. You receive an alert on the Plesk Homepage. Plesk also creates default reports based on the statistics for this period.

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

Note for Windows hosting administrators:

In Plesk for Windows, you can use limitations on outgoing email messages if you think you need to. Before you configure 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 – check that the option Allow Plesk to send email notifications through this SMTP server is turned on.

Antivirus settings and Plesk mail spam protection

Antivirus settings and Plesk mail spam protection

Choose the antivirus program that you want to use on the server. For details, see Antivirus Software.

You can also pick the spam protection options that you want to use on the server. If you want to use spam protection systems, such as SpamAssassin spam filter. Or protection systems based on DKIM, DNS Blackhole Lists or Sender Policy Framework (SPF). Go to the Antispam Tools section.

Names for POP3/IMAP mail accounts

Names for POP3/IMAP mail accounts

When using the Qmail mail server, you can choose this mail account format.

If you select the Use of short and full names is allowed option. Users can log in to their mail accounts using just the left part of their email address. This is the bit before the @ sign (for example, username). Or by using the whole email address (for example, [email protected]).

To avoid difficulties for email users who are in different domains, but share identical usernames and passwords. Think smart and use the Only use of full mail account names is allowed option.

Once you set your mail server to only support full mail account names, you won’t be able to switch back to supporting short account names. At least, not until you’ve ensured there aren’t any encrypted passwords for mailboxes and user accounts with the same usernames and passwords residing in different domains.

We hope this detailed guide to mail configuration helps you improve your current set-up. We want you to get the most out of your Plesk mail server.

Let us know if this guide helped in the comments below.

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Elvis Plesky
Our fun and curious team mascot's always plugged into the latest trends. He's here to share his knowledge and help you solve your tech problems.
    Showing 2 comments
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      every time when i sending an email containing a 17 mg ziped attached file ,getting a failure notice from yahoo with title of message is to big .
      how can i fix it?

      • Laura from Plesk
        Laura from Plesk

        Hi Jaber! Could you address your issue to our support channel, please? Our support team will be able to help you with it. Thank you!

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