Most threads that take a week take a week because the first five replies were spent establishing which version is running. Paste the block below at the top of your post, fill it in, and the first reply you get can be an answer.

The template

hMailServer version: 6.3.8.47 (Windows) or the exact package version (Linux)
Platform: e.g. Windows Server 2022, Ubuntu 24.04 x86-64, Debian 12 AArch64
Database: PostgreSQL 16 / MariaDB 11 / MySQL / built-in
How it got here: fresh install, or in-place upgrade from 5.6.8 on 12 September 2026
Control Deck, webmail or REST API enabled: yes or no (RestApiPort set)
Anti-spam in use: SpamAssassin, SURBL, DNSBLs, greylisting
What I expected to happen:
What happened instead:
First seen: date and time, and what changed immediately before that
Already tried:
Log excerpt, timestamps intact and credentials redacted:

Version, exactly

Three parts and the build stamp, not the latest. 6.3.8 and 6.3.8.47 are different things to say, and 6.2.24 or earlier is a real answer if that is where you are. If you are not sure, the version is on the Control Panel dashboard on Windows and in the Control Deck at / on either platform.

Logs beat descriptions

Raise the log level before you reproduce the fault, reproduce it once, then take the window around it — the SMTP, IMAP, POP3 or application log as applicable. Leave the timestamps in; they are how anyone reading works out ordering. Paste it in a fenced code block rather than as a screenshot, and strip the AUTH lines, API tokens, DKIM private keys and third-party addresses first: the forum is public and indexed, and a credential pasted here is a credential to rotate.

Check these before you post

• Is it fixed already. Every hMailServer 6 release lists exactly what changed: see the release notes on the downloads page and the pinned release history in Announcements & releases.
• Is it the upgrade. Any 5.3 to 6.3.7 goes straight to 6.3.8, but for the original hMailServer's 5.7, which 6.3.8's installer refuses (move its mail over IMAP instead): from 6.3.4 to 6.3.7 by the live update, with the exceptions the 6.3.8 announcement lists under Upgrading, from anything older by hand. The schema upgrade to 6108 is one-way, so back up first. On MySQL or MariaDB it needs MySQL 5.7.9 or MariaDB 10.2.2 or later and the ALTER privilege: the upgrade chapter.
• Is it DNS. It is very often DNS — DNS and deliverability.
• Is it certificates or transport security. TLS 1.2 and 1.3 only, with MTA-STS, DANE and DNSSEC validation enforced by default for outbound mail — encryption and certificates.
• Is it a platform limit. No Control Panel and no COM on Linux, and event scripts there run in JavaScript only; the Linux packages from 6.3.6 on are for x86-64 and AArch64, 6.3.4's and 6.3.5's were x86-64 only — the Linux chapter.

Where things live

• The webmail and the Control Deck — chapter 36
• The REST API — chapter 24
• Rules and Sieve — chapter 12
• Monitoring and health — chapter 16
• Security hardening — chapter 17
• Version history — chapter 25

Then post it in the right place

Mail not arriving and queues go in General support, installs and upgrades in Installation, migration & upgrades, certificates and deliverability in TLS, certificates & deliverability, and Linux-specific problems in Linux. COM and scripts go in Scripting & the COM API, the REST API in REST API & integrations, and filtering in Anti-spam & message filtering. Something you want built goes in Feature requests. A reproducible defect goes on GitLab, linked from the thread. Without a GitLab account, email it, with a link to the thread, to the project's Service Desk address, contact-project+hmailserver-hmailserver-86730559-issue-@incoming.gitlab.com: GitLab files the message as a confidential issue, which only the maintainers see, and their replies reach you by email.

If the answer turns out to be interesting, write it up afterwards in Guides & tutorials. That category is how this forum stops being the same twenty questions.