What Is Lotus Notes? HCL Notes, Domino and NSF Files in Plain English
Lotus Notes is the work email and database program that IBM sold to HCL. Learn what the names mean, how NSF files and replication work and how to open your data.
Lotus Notes is the work email and database program that IBM sold to HCL. Learn what the names mean, how NSF files and replication work and how to open your data.
Lotus Notes is a business email and database program that now goes by HCL Notes. Notes is the client on your desktop. Domino is the server that stores the mail and shares the data.
Everything lives in NSF files. One NSF holds the design and the documents plus the access list and a replica ID. That is why HCL Notes can copy a mail file to your laptop and merge your changes later.
HCL owns it, sells it and updates it today. Version 14.5.1 shipped in March 2026. You open an NSF in the Lotus Notes client. You need the matching ID file to read anything protected.
Lotus Notes is a desktop program for work email, calendars, contacts and shared databases. Lotus Development released it in 1989. Today HCL sells the same product as HCL Notes.
Most people meet Lotus Notes as a mail client. Under the mail sits a bigger idea. Lotus Notes stores information as documents in databases and lets teams build forms and views on top.
A department can keep an approvals form and a customer log next to its mail. Both open from one workspace and share one login. That mix explains how Lotus Notes outlived most of its early rivals.
Lotus Notes email sits beside a group calendar and a to do list. The client also keeps contacts and can browse the web. Replicated databases let you work offline.
HCL Notes today comes in two halves. The client sits on your desktop and the HCL Domino server holds the shared data. The two together make up what people still call Lotus Notes.
HCL markets its newest release as HCL Domino 2026 with the version number 14.5.1. The history of the names appears in section 2.
Notes is the client. Domino is the server. An NSF file is the database that both of them read.
.nsf with .ntf for templatesComing from the Microsoft side? Microsoft Outlook and Exchange Server cover the mail world that Lotus Notes users compare against.
All three names mean one product line. Lotus, IBM and HCL held it in sequence. The owner of the day set the name.
Iris Associates wrote Notes under contract. Iris formed in 1984 and Lotus bought the company in 1994. Lotus Development shipped Release 1 in December 1989.
IBM bought Lotus in 1995 to get Lotus Notes. Sources disagree on the price. This page states no figure.
Release 4.5 arrived in December 1996 and gave the server its own name. Domino became the server while only the client kept the Lotus Notes name.
IBM announced in November 2012 that it would drop the Lotus brand. Notes and Domino 9.0 Social Edition followed on 21 March 2013. The product became known as IBM Notes.
IBM announced the sale on 6 December 2018 for 1.8 billion dollars. The deal covered Notes and Domino plus related collaboration software. It closed in mid 2019.
HCL shipped version 11 in December 2019 and version 12 on 7 June 2021. Version 14 followed on 7 December 2023 and version 14.5 on 17 June 2025. Version 14.5.1 arrived in March 2026.
| Period | Client name | Server name | Owner |
|---|---|---|---|
| 1989 to 1996 | Lotus Notes | Lotus Notes | Lotus Development then IBM from 1995 |
| 1996 to 2012 | Lotus Notes | Lotus Domino | IBM |
| 2013 to 2018 | IBM Notes | IBM Domino | IBM |
| 2019 onward | HCL Notes | HCL Domino | HCL |
Menus and help pages in the current client say HCL Notes. Older articles and many search results still say Lotus Notes or IBM Notes. All three describe one codebase that grew over nearly four decades.
A search for any of the three names lands on the same software. Select the name that matches the version on your screen and you find the right help pages.
Looking for the email programs from this era? Mozilla Thunderbird and Microsoft Outlook sit in the same email application guides.
Domino stores and routes. HCL Notes displays. Your mail file lives on the server. Lotus Notes opens it from there or from a local copy.
Domino is the server half of Lotus Notes. It stores mail files and shared databases. It also moves messages between people while the Lotus Notes client shows you the results.
Domino speaks SMTP and MIME for mail and offers POP3 and IMAP to other mail programs. Its HTTP task converts documents into web pages and can act as a web server. That is why some HCL Notes data appears in a browser.
HCL Notes can also work as an IMAP or POP client for servers that are not Domino. Your Lotus Notes mail window can show a mailbox that sits on another system.
Domino servers can join a cluster. Clustering has given Domino copies in separate places since Release 5. When one server fails a second server still holds the same database.
| Component | Job | Platforms |
|---|---|---|
| HCL Notes client | Mail, calendar, contacts and apps | Windows, macOS and Linux |
| Domino server | Stores databases and routes mail | Windows, Linux, AIX and IBM i |
| Domino Designer | Builds and edits applications | Windows only |
Developers write Lotus Notes apps in Formula, LotusScript, Java and JavaScript. HCL also ships REST interfaces plus toolkits for C, C++ and Java.
Lotus Notes email depends on this split. The server holds your mail file and the client shows it. Switch computers and your messages stay on the server.
The Domino Directory is an NSF too. It carries the file name names.nsf and holds the administration ECL. Domino itself depends on the same format it serves to you.
Domino IQ arrived with version 14.5 in June 2025. HCL describes it as AI that works with private language models inside your own network. With fix pack 1 for 14.5.1 retrieval augmented generation works in local and remote modes.
HCL pitches Domino IQ as a way to ask questions of your own Domino databases in plain language.
NSF is the Notes Storage Facility. One NSF is an entire database with design and documents inside the same file.
NSF stands for Notes Storage Facility. HCL treats the NSF as the standard storage format for Notes and Domino. It is a document database file that holds the application design and its data together.
Your mail file is an NSF. So are your bookmarks in bookmark.nsf and your contacts in names.nsf. Templates use the .ntf extension while applications use .nsf, as the HCL overview of Notes applications explains.
A document holds fields with your values. A form decides how those fields look on screen. A view lists documents in rows. The inbox in a mail file is a view.
Design and data share one file. Move the NSF and the forms, views and access list move with it.
Every NSF carries a replica ID. Copies that share the ID count as replicas of one database. Copies with different IDs count as different databases even when the titles match.
Section 5 shows how replicas use that ID. A mismatch is the first thing to check when two copies refuse to sync.
Lotus Notes email lives in your mail file. That file is an NSF on the Domino server. The Lotus Notes client opens it as an application with an inbox view and a calendar view.
If you made a local replica then a second copy sits on your computer. HCL lists that local mail file by your name with the .nsf extension.
A PST file stores your Outlook messages and folders in one local file. An NSF carries the same kind of items plus the design and the access list. The PST files guide covers the Outlook side.
Lotus Notes treats every NSF as an application. A mail file is one application and a customer log is another. Both use the same file type.
Replication keeps replicas in step. Every replica shares a replica ID. Lotus Notes passes along changed fields instead of entire files.
A replica is a duplicate of an HCL Notes application. HCL says the local version is identical to the application on a server. Changes in either copy reach the other. The HCL replication quick reference covers the menu paths.
A local replica opens much faster than the server version. You can also work on it with no network. When you reconnect, Lotus Notes trades the changes.
File > Application > Make Available Offline to create the replica.
Replication began at document level. Notes 4 in 1996 moved it to field level. If you change one field and a coworker changes another field in the same document then both edits can survive.
HCL documents say replication transfers only changes to a database. Connection documents hold the schedules. Administrators can also start a session by hand through server commands.
A replication conflict occurs when two or more users edit the same document in different replicas. A save conflict occurs when two users edit it in the same application on a server.
HCL Notes marks the losing version as a response with a diamond symbol in the left margin. You review both versions and delete the one you do not need.
In a replication conflict the document with the greatest number of edits and saves becomes the main one. A tie goes to the document saved last. A save conflict keeps the document saved first. The HCL guide to replication and save conflicts lists the full rules.
The ID file is who you are. The ACL is what you can do in one database. The ECL is what code can do on your computer.
Three separate controls guard Lotus Notes data. The ID file proves who you are. The access control list sets what you can do in one database. The execution control list sets what code can do on your workstation.
Domino uses ID files to identify users and to control access to servers. Domino creates one when it registers you. The HCL documentation on ID files lists your name, a license number, at least one Notes certificate and a private key.
The private key lets you sign messages and read mail sent to you. The file can also hold Internet certificates and secret keys for field encryption. A password protects it. A key derived from that password encrypts the data inside.
Your ID file is named after you and ends in .ID. It sits in your HCL Notes data directory apart from your mail NSF. HCL lists it first among the files you need to back up.
Lotus Notes uses all three together. Lose one and the other two cannot help you. The ID file opens the door. The ACL decides which rooms you enter.
An ID vault is an optional server database that holds protected copies of Notes user IDs. The HCL documentation on ID files strongly recommends it for ID recovery. The older recovery feature still works.
| Level | What it allows |
|---|---|
| Manager | Changes the ACL plus encryption and replication settings. Can delete the database |
| Designer | Changes all design elements |
| Editor | Creates documents and edits every document including those from other people |
| Author | Edits documents that name the user in an Authors field and creates documents when allowed |
| Reader | Reads documents where a Readers field names the user |
| Depositor | Creates documents with no other access |
| No Access | Opens nothing except public documents the database allows |
The ACL lives inside the NSF. It travels with every replica. Only a user with Manager access can change it. The HCL list of ACL access levels gives the full wording.
An execution control list protects your workstation. It decides whether the signer of a piece of code can start it on your machine. If the signer is missing from the list then HCL Notes shows an Execution Security Alert and you choose how to respond. See the HCL page on the execution control list.
Two kinds exist. The administration ECL sits in the Domino Directory and serves as the template. Your workstation keeps its own copy in your contacts file.
Encryption has grown over time. Notes 11.0.1 added 128 bit AES for local database encryption. Domino 12.0.2 added 256 bit AES as an option.
Notes and Domino ship as a pair with app building included. Outlook and Exchange are two Microsoft products that share the mail job.
Lotus Notes pairs a client with a server and adds an app builder. Outlook is a client while Exchange Server is the matching server. Microsoft sells them as two products that work together.
Outlook is a desktop email client and personal information manager. It sends and receives mail and keeps a calendar plus contacts and notes. Exchange stores mail and calendars for many users on a server.
| Question | HCL Notes and Domino | Outlook and Exchange |
|---|---|---|
| Client | HCL Notes | Microsoft Outlook |
| Server | HCL Domino | Microsoft Exchange Server |
| Server database file | NSF | EDB |
| Offline copy | Local replica as another NSF with the same replica ID | OST file that caches server folders |
| Standalone local file | Any NSF kept on your computer | PST file |
| Mail protocols | SMTP, POP3 and IMAP on Domino | POP3, IMAP and SMTP accounts in Outlook |
| Current seller | HCL | Microsoft |
Lotus Notes email and Outlook email feel alike in daily use. You write a message and send it. You file it in a folder. The difference sits in the file under the hood.
No. Outlook keeps its local items in PST and OST files. It does not use NSF. Read the PST files guide and the OST files guide to see what Outlook expects.
On the server side Exchange stores mail in EDB files. The EDB files page explains that format.
Moving mail between the two systems is a migration job. Lotus Notes can export a view to a text or CSV file as section 9 shows. That gives you rows of data. It does not give you a finished Outlook mailbox.
HCL supports Notes today. Version 14.5.1 shipped in March 2026 and a fix pack followed in July 2026.
Yes. HCL still builds and sells HCL Notes and supports it. HCL announced version 14.5.1 on 19 March 2026 under the name HCL Domino 2026. Fix pack 1 followed on 16 July 2026. See the HCL announcement of version 14.5.1 and the HCL notice for fix pack 1.
HCL says version 14.5.1 brings a refreshed HCL Notes interface plus an improved workspace and calendar. OIDC sign in joins the client. The server side gains better performance and stronger security.
| Release | Date | Note |
|---|---|---|
| 9.0 Social Edition | 21 March 2013 | Shipped after IBM dropped the Lotus brand |
| 10.0 | 10 October 2018 | Last release before the HCL sale |
| 11.0 | 12 December 2019 | First HCL release |
| 12.0 | 7 June 2021 | Release 12.0.2 added OIDC login and a 256 bit AES option |
| 14.0 | 7 December 2023 | Named the latest release in the HCL notice for version 11 |
| 14.5 | 17 June 2025 | Introduced Domino IQ |
| 14.5.1 | 19 March 2026 | Sold as HCL Domino 2026 |
| 14.5.1 FP1 | 16 July 2026 | Fix pack for all 14.5.1 customers |
IBM Notes 9 and 10 customers face a choice. They can pay for Extended Support or move to HCL Notes 14.5.1. The dates follow below.
HCL keeps two versions under active support at any time. Version 11.0.x reached end of support on 26 June 2025. The HCL notice on version 11 end of support sets out the dates.
Versions 9, 10 and 11 qualify for paid Extended Support through 30 June 2030. HCL requires Standard Support first. It arranges the extension through a statement of work. Read the HCL notice on Extended Support for the terms.
The Register reported that many customers have stayed on versions 9 and 10. HCL keeps supporting them for a fee. HCL also encourages customers to move to the latest release.
No verified count of current Lotus Notes users appears on HCL pages. This page gives none. Check the HCL product lifecycle page for the date that applies to your version.
Open an NSF from inside Notes with File > Open > Notes Application. Without the client and your ID file the NSF stays closed.
You need the Lotus Notes client to open an NSF. Install HCL Notes and sign in with your ID file. Then open the file from the menu. Double clicking works only after the client is installed. The HCL steps for opening an application confirms the path.
File > Open > Notes Application. Notes Basic users select File > Application > Open.On My computer if the NSF sits on a local drive.HCL Notes asks for your ID password at start. A wrong password stops the session before any NSF opens. That is why the ID file matters more than the database.
Two checks decide whether the file opens. Your ID must match the file. Your ACL level must sit above No Access.
Lotus Notes can export a view in four forms. HCL lists CSV, worksheet, tabular text and structured text. PST is not on that list. The HCL steps for exporting views shows every option.
Domino also has DXL, the XML form of Domino data. The HCL overview of DXL says it describes embedded views, forms and documents. Developers use it to move design and data in and out of an application.
Three HCL tools read an NSF directly. They are the Notes client, the Domino server and Domino Designer. When you cannot install the client then ask your administrator for a CSV or structured text export.
Administrators handle full mailbox moves. They use Domino and Microsoft migration paths. This page names no third party converter. For the Outlook side see Outlook PST data and MBOX files.
Check the ID first. Check the ACL second. Check the file third. Most lockouts end at one of the first two.
Three faults look alike on screen. The fixes differ. The right one depends on whether you are a user or an administrator.
Start with the cheapest check. Open another application in HCL Notes. If it opens then the ID file works and the fault sits in one database.
Check for a vault before you panic. Open User Security and look at the Security Basics tab. The HCL steps for recovering a user ID says it reads "This ID file has been backed up into vault" followed by the vault name.
Without a vault recovery works only when administrators set up recovery information in advance. An encrypted backup alone does not work with Notes until the owner recovers it. You also need the recovery passwords from your administrators. The HCL steps for recovering a user ID lists every step.
Certifier IDs cannot be recovered. Only user IDs can.
Domino administrators type these commands at the server console. HCL names Fixup for views and documents. It names Updall for views and full text indexes. It names Compact with the -c option for damage that Fixup cannot correct. See the HCL page on fixing corrupted databases.
load updall -R database.nsf to rebuild every view.load fixup -f database.nsf. The -f option checks all documents. The HCL page on Fixup switches lists more switches.load compact -c database.nsf. Nobody can use the database during this task. The disk needs free space for the copy.Users can rebuild one view with Shift and F9. Ctrl and Shift and F9 rebuilds every view. A fresh replica from a healthy copy also works.
Fixup does not apply to databases that use transaction logging. HCL Notes recovers those from the log. Server crashes damage NSF files. So do file moves on a live server and disk faults.
NSF is a database format and not a mail format. One NSF can hold mail or a policy library or a customer log.
HCL documents NSF through its tools and programming interfaces. The sources checked here do not publish a byte by byte layout. What follows covers the parts HCL does describe.
.nsf.ntf| File | What it holds |
|---|---|
yourname.ID | Your user ID file. You need it to access Notes |
yourname.nsf | Local copy of your mail, calendar and to do list |
names.nsf | Your contacts, mailing groups, connections and locations |
bookmark.nsf | Saved bookmarks and Home Page information |
desktop8.ndk | Your workspace, which maps to your bookmarks |
notes.ini | Settings you gave Notes at setup |
HCL warns that its table can be incomplete or outdated. Compare it with your own data directory. Copy the ID file first. Without it the other files stay locked.
Want the wider picture of how formats work? Read what a file format is and browse the file format guides.
Check for an ID vault. Section 10 walks through vault and recovery.
Ask a database Manager. Section 6 lists the seven ACL levels.
Is the other side Outlook? PST files and OST files cover the files Outlook uses. Microsoft Outlook explains the client itself.
Does your mail move to a Microsoft server? EDB files describe Exchange databases. Exchange Server covers the server. OLK files cover Outlook for Mac.
Want another groupware server to compare? Zarafa is one. Zimbra and MDaemon are two more mail servers.
Leaving for a desktop client? Mozilla Thunderbird stores mail in MBOX files and old contacts in MAB address books. Apple Mail and Windows Mail use their own stores.
Need to carry calendar entries? ICS files move events between calendar programs. For the basics read what a file format is. Then browse the file format guides or the email application guides.
Is the fault in the machine instead? Our Windows error guides and macOS guides start from the message on screen. Browse the FileFix category index for everything else. The FileFix home page shows what is new. Send us the file details if your NSF acts in a way this page does not explain.