Plesk extension

Mailbox Storage Inspector

See exactly which folder is using the space in a mailbox — and fix the quota accounting when it lies.

Plesk 18.0.40+UnixAdmin onlyRead-onlyv1.0.0

A ticket that says “my mailbox is full”

Plesk reports one number per mailbox. When a customer says the mailbox is full but only a fraction of the quota is in use, or when a mailbox is genuinely full and nobody knows which folder to blame, that single number answers nothing. Support ends up guessing: is it an archive folder, a runaway mailing list, a stuck tmp/ directory, or a maildirsize file that has drifted from reality?

This extension answers those questions in one screen. It scans the mailbox through Plesk’s own long-task runner, breaks the storage down folder by folder, and compares what Dovecot believes against what is actually on disk.

What it does

Folder-level breakdown

Every folder with its message count, actual message bytes and share of the mailbox, sorted largest first.

Comparison, not a single figure

Folder totals sit beside maildirsize, doveadm quota and the on-disk total, so a mismatch is visible rather than inferred.

Stale accounting warnings

Flags quota drift, duplicate INBOX.* folders, oversized tmp/ directories, and folders holding more files than Dovecot accounts for.

One-click quota reset

Rebuilds maildirsize with a backup first, then doveadm quota recalc and a plesk repair mail fallback if needed.

CSV for the ticket

Exports the folder table with a UTF-8 BOM and formula-injection protection, so it pastes cleanly into a support thread.

Audit trail

Every reset is written to Plesk’s Action Log as Mailbox usage reset, with the mailbox and the before/after totals.

Designed for support work

Admin-only by design. Resellers and customers cannot open it. Mailbox investigations land with the people who can actually fix them.
Nothing is modified by default. Scanning is read-only. The only write action is the explicit quota reset, and it refuses to run while a scan of the same mailbox is in progress.
Results stay local. Scan output is cached on the server under var/modules/mailbox-storage-inspector/. No telemetry, no external API, no message content ever read.
Cached results are honest about their age. Stale data is labelled, mailboxes up to 5 GB refresh quietly in the background, and larger ones wait for a button press.

Requirements

Plesk 18.0.40 or later on a Unix server, with Dovecot mail as managed by Plesk.

Access administrator level. The scan and reset helpers run as root through pm_ApiCli::callSbin() because the panel user cannot read Dovecot’s auth socket.

Not supported on Windows hosting, or on servers where mail is served by something other than Dovecot under Plesk management.

Install

Download the ZIP, then either upload it under Extensions › My Extensions › Upload Extension, or install it from the command line:

plesk bin extension --install mailbox-storage-inspector-1.0.0.zip

Upgrade by uploading a newer ZIP over the installed version. Remove it with plesk bin extension --uninstall mailbox-storage-inspector, which also deletes its runtime data directory.