diff --git a/pkgs/development/ocaml-modules/letters/default.nix b/pkgs/development/ocaml-modules/letters/default.nix
new file mode 100644
index 000000000000..e3588c3a21d7
--- /dev/null
+++ b/pkgs/development/ocaml-modules/letters/default.nix
@@ -0,0 +1,58 @@
+{
+  alcotest-lwt,
+  buildDunePackage,
+  ca-certs,
+  colombe,
+  containers,
+  domain-name,
+  emile,
+  fetchFromGitHub,
+  fmt,
+  lib,
+  logs,
+  lwt,
+  mrmime,
+  ptime,
+  rresult,
+  sendmail,
+  tls-lwt,
+  x509,
+}:
+
+let
+  pname = "letters";
+  version = "0.4.0";
+in
+buildDunePackage {
+  inherit pname version;
+  src = fetchFromGitHub {
+    owner = "oxidizing";
+    repo = "letters";
+    tag = version;
+    hash = "sha256-75uLg+0AVDNdQ0M4w8H7MrTYwAKMhe8R5xC4vPNGkuQ=";
+  };
+  propagatedBuildInputs = [
+    ca-certs
+    colombe
+    containers
+    domain-name
+    emile
+    fmt
+    logs
+    lwt
+    mrmime
+    ptime
+    rresult
+    sendmail
+    tls-lwt
+    x509
+  ];
+  doCheck = true;
+  checkInputs = [ alcotest-lwt ];
+  meta = {
+    description = "OCaml library for creating and sending emails over SMTP using LWT";
+    homepage = "https://github.com/oxidizing/letters";
+    license = lib.licenses.mit;
+    maintainers = [ lib.maintainers.vog ];
+  };
+}
diff --git a/pkgs/top-level/ocaml-packages.nix b/pkgs/top-level/ocaml-packages.nix
index 8574d7e5816b..219e0efe8aea 100644
--- a/pkgs/top-level/ocaml-packages.nix
+++ b/pkgs/top-level/ocaml-packages.nix
@@ -1127,6 +1127,8 @@ let
 
         letsencrypt-mirage = callPackage ../development/ocaml-modules/letsencrypt/mirage.nix { };
 
+        letters = callPackage ../development/ocaml-modules/letters { };
+
         libc = callPackage ../development/ocaml-modules/libc { };
 
         lilv = callPackage ../development/ocaml-modules/lilv {