Plesk's Mail Server Settings control how the whole server sends and receives email. Sensible values here stop open relays, reduce spam, and help legitimate mail get delivered. This guide walks through the important options for administrators.
Before you start
- Plesk administrator access.
- A valid hostname and reverse DNS for the server IP; see hostname and panel SSL.
Open the settings
Go to Tools & Settings → Mail Server Settings (under Mail). The Settings tab holds server-wide options; other tabs cover the queue, black and white lists, and spam filtering.
Core settings
- Enable mail management functions in Plesk – keep on unless DNS and mail are hosted elsewhere for all domains.
- Maximum message size – for example 25–50 MB; larger limits encourage using email for file transfer.
- Enable SMTP service on port 587 – required for submission; most clients use 587 or 465.
- Relaying – choose authorization is required with SMTP authentication. Never set open, which turns the server into a spam relay.
- Mailbox format and name – allow short names only if no two domains share user names.
Spam and abuse protection
- Greylisting: temporarily rejects mail from unknown senders; real servers retry, many spam tools do not. Enable it on the Spam Filter tab or via the greylisting settings.
- DNS blackhole lists: tick Switch on spam protection based on DNS blackhole lists and add zones such as
zen.spamhaus.org. - SPF checks on incoming mail: tick Switch on SPF spam protection with a mode such as Reject mail when SPF resolves to fail.
- DKIM: allow signing outgoing mail and verifying incoming mail; see SPF, DKIM and DMARC.
- Outgoing mail limits: cap messages per hour per mailbox and subscription; see mail queue troubleshooting.
Outgoing mail mode
Choose which IP addresses send mail: Send from domain IP addresses (each domain uses its own IP), Send from the specified IP address (one clean IP for everything), or use a Smart host relay when your provider blocks port 25 or you route mail through a delivery service.
Webmail
Under Tools & Settings → Webmail (or Updates → components), choose the default webmail application – Roundcube is standard. Customers reach it at webmail.example.com once DNS and SSL are in place.
Black and white lists
The White List tab lists networks allowed to relay without authentication – keep it to 127.0.0.1 and your own servers. The Black List blocks domains from sending to you.
Troubleshooting
- Clients cannot send: port 587 disabled or authentication settings wrong.
- Legitimate mail delayed: greylisting delays first messages by minutes; whitelist important partners.
- Server listed as spam source: check for open relay, compromised mailboxes or scripts, and outgoing limits.