Mail flow rules
Tag mail from outside, add a disclaimer, block risky attachments, copy or redirect someone's mail. Try a rule in test mode first.
Version 0.9.0
Exchange's features. Your own server.
Obsidian Mail Server gives your organization mail, calendars and contacts on phones, Macs, Outlook and the web, all from one server you control. It comes with an admin center that walks you through setup, compliance tools for regulated work, and its own installable appliance. Run it on your own hardware, or let us host it for you.
- Exchange ActiveSync · EWS · IMAP
- Webmail included
- Installer ISO & VM images
- Signed updates
Speaks
Exchange ActiveSync
Exchange Web Services
MAPI over HTTP (preview)
IMAP, POP3 & SMTP
01Every app
The apps people already use
The server speaks the same protocols as Exchange, so the mail apps on phones, Macs and PCs connect to it as an Exchange account. People type their address and password; Autodiscover finds the server.
Phones & tablets
Exchange ActiveSync 12.1 to 14.1: mail, calendar, contacts and tasks with push, meeting replies, device policies and remote wipe.
Mac
Exchange Web Services for Apple Mail, Calendar and Contacts and Outlook for Mac: folders, sync, notifications, free/busy and automatic replies.
Outlook for Windows
MAPI over HTTP for classic Outlook, in online and cached mode, with the offline address book and NTLM sign-in. In preview, switched on per user.
Any mail app
IMAP with IDLE, CONDSTORE, QRESYNC and MOVE, POP3, and SMTP submission. Thunderbird and others set themselves up from the address.
Webmail and calendar included
Every mailbox can also be used in the browser, with nothing to install. Messages are cleaned before they are shown, and pictures from the internet stay off until the reader asks for them.
- Conversations or single messages, with color categories shared with phones and Outlook.
- Calendar by day, week or month. Invitations arrive as tentative events, replies update the organizer, and rooms book themselves when they are free.
- People: the organization's address book and your own contacts.
- Inbox rules and automatic replies that run on the server, so they work with every device switched off.
- Shared mailboxes like info@ and support@, opened from your own mailbox, with send as and send on behalf.
- Recover deleted items for 14 days after the Deleted Items folder is emptied.
- Online archive and public folders, with folder roles from owner to reviewer.
- Four looks: Cut Obsidian, Swiss Precision, Tactical SOC and Daylight.
Also on Windows: Obsidian Mail Client connects to the server over Exchange ActiveSync, with new mail the moment it arrives.
02Admin center
An admin center that tells you what to do next
No consoles of cmdlets to learn. The admin center checks your setup itself, says what is missing in plain language, and links to the right page of its built-in administrator's guide.
- A setup guide that checks itself. The server's name, DNS records, MX, Autodiscover, SPF, DKIM and the certificate are looked up live and ticked off as they work.
- Common tasks one click away: add a user, reset a password, create a shared mailbox or a group, block a lost phone.
- Users and groups, shared mailboxes, rooms and equipment, contacts, and who may open or send from which mailbox.
- Track a message through the server, see the queue, and set up outgoing routes.
- Administrator roles: global, organization, helpdesk, view-only and discovery manager, with every change in the change history.
- Several organizations on one server, each with its own domains and administrators.
- Free certificates from Let's Encrypt, and a command line,
oms, for everything the admin center does.
Phones & tablets
Every device that syncs, its policy, and buttons to block it or erase it if it is lost.
Quotas
Mailbox size limits with warnings to the person before they are reached.
Built-in guide
Installation, DNS, certificates, apps, mail flow, backups and troubleshooting, filled in with your server's own names.
Sign-in protection
Passwords stored with Argon2id, and guessing slowed down after 10 wrong passwords within 15 minutes.
DKIM signing
Create a key, publish one DNS record and turn signing on, so mail reaches inboxes at Gmail and Outlook.com.
Soon
Active Directory
Import users and groups from Active Directory, keep them in sync, and sign in with the AD password.
03Compliance
Ready for regulated work
The tools Exchange administrators rely on for legal, healthcare and finance, built in and managed from the same admin center.
Data loss prevention
Finds card numbers, SSNs, IBANs, secret keys and health identifiers, also inside Office attachments. HIPAA template included.
Journaling
A report of every message a rule covers, naming everyone who really received it, Bcc and group members included, sent to an archive.
Retention policies
Tags that delete or archive mail after a set time, on folders or single messages, applied on the server.
Litigation & query holds
Keep everything a person has, or everything matching a search, even when it is deleted or purged.
eDiscovery
Cases with searches across mailboxes, archives and recovered items, preview, case holds and a ZIP export with a SHA-256 manifest.
Mailbox audit log
Who opened, moved, deleted or sent from which mailbox, from webmail, phones, Outlook or IMAP, including administrators and delegates.
Discovery manager
A role for legal staff: run searches and holds without being able to change anything else.
04Appliance
A whole server, not a list of prerequisites
Obsidian Mail Server is its own small operating system, built on Ubuntu Server 24.04 LTS with PostgreSQL. There is nothing to install first: start it, answer a few questions on the console, and sign in to the admin center.
Install
Running in minutes
- Start the imageThe installer ISO for a physical server, a Hyper-V disk with a script that creates the VM, or an OVA for VMware.
- Answer the setupHost name, network, time zone, a password, the firewall, and your first organization with its administrator.
- Follow the guideThe admin center's setup guide shows the DNS records to create and checks them as you go.
Run
The server's own tools
- NetworkAddresses, DNS and the firewall. A change undoes itself unless you confirm it still works.
- StorageGrow the disk or add one, and move the mail onto it, from the browser.
- BackupsScheduled to a Windows share, an NFS export or another disk, and restored from the same page.
- Updates and diagnosticsSigned updates, logs, connectivity tests and a support bundle with passwords removed.
.NET 10PostgreSQL 16Ubuntu Server 24.04 LTSMimeKitArgon2idLet's EncryptSigned apt updates
05Yours or ours
Run it yourself, or have us run it
The same server either way. Choose where it lives.
On your servers
Self-hosted
Install the appliance on your own hardware or virtualization. Your mail never leaves your network unless it is addressed elsewhere, and you decide when to update.
Download
On ours
Hosted by Larström
We run the server, its updates and its backups for you. You manage your people and settings in the same admin center, and point your domain's records at us.
Talk to us
06Download
Get Obsidian Mail Server
Version 0.9.0. Once installed, it updates from our signed repository.
Downloads ask for a user name and password. Ask us for access.
Physical or any VM
Installer ISO
Start a server or a virtual machine from it. It asks for the network and the disk, and needs no internet connection to install.
Download the ISO
Hyper-V
VHDX disk
A ready-made disk for a Generation 2 VM with Secure Boot. New-ObsidianVM.ps1 creates and starts the VM.
VMware
OVA appliance
Deploy it in vSphere, or open it in Workstation or Fusion, choose the network and start it.
Download the OVA
Ubuntu Server 24.04
Package
For an existing Ubuntu Server 24.04 machine. Installing it also adds our signed update repository.
Download the .deb4 CPU cores, 8 GB of memory and 64 GB of disk serve a few hundred mailboxes; give mail more disk as it grows. 64-bit x86. SHA-256 checksums
07Questions
Frequently asked
Is this Microsoft Exchange?
No. Obsidian Mail Server is our own server, written in .NET. It speaks Exchange's protocols, which is why phones, Macs and Outlook connect to it as an Exchange account, and it follows Exchange's ideas so administrators find their way around: recipients, connectors, mail flow rules, retention and holds.
Does it work with classic Outlook for Windows?
Classic Outlook connects over MAPI over HTTP, in online and cached mode, with the offline address book. It is in preview: an administrator switches it on per user with oms mapihttp enable, and Windows sign-in with NTLM is switched on with oms ntlm enable. Everyone else uses Exchange ActiveSync, EWS or IMAP, which are on for all.
Does it filter spam and viruses?
Not by itself. Put a filtering gateway in front of it, such as Obsidian Suite, our email security service: it filters incoming mail and hands the clean mail to your server. The server reads the spam verdict a gateway adds and files tagged mail in Junk Email.
What do I need to run it?
A physical server or a virtual machine on Hyper-V, VMware or another hypervisor. 4 CPU cores, 8 GB of memory and 64 GB of disk are enough for a few hundred mailboxes. You also need a domain whose DNS records you can change, and, to receive mail from the internet, a public address for port 25.
How are updates delivered?
From our apt repository, signed with our own key. The package sets up the repository with our key pinned to it, so an update is accepted only when we signed it. Updates are installed from the admin center or the console when you choose.
Can I move my mailboxes over from Exchange?
Importing mailboxes straight from an Exchange server is planned. Until then you can create the mailboxes and move mail with the tools you would use between any two mail servers.
What does hosting cost?
It depends on the number of mailboxes and what you need. Contact us and we will tell you.
Keep spam out before it arrives
Obsidian Suite filters mail for your server, Microsoft 365 and Google Workspace before it reaches anyone's inbox, with an AI model that explains every decision.