diff --git a/modules/misc/news.nix b/modules/misc/news.nix
index 99c2de5cc..f87daed81 100644
--- a/modules/misc/news.nix
+++ b/modules/misc/news.nix
@@ -690,6 +690,13 @@ in
           appreciated, both positive and negative.
         '';
       }
+
+      {
+        time = "2018-07-01T16:07:04+00:00";
+        message = ''
+          A new module is available: 'programs.mbsync'.
+        '';
+      }
     ];
   };
 }
diff --git a/modules/modules.nix b/modules/modules.nix
index 6229ec4b5..312c9c971 100644
--- a/modules/modules.nix
+++ b/modules/modules.nix
@@ -41,6 +41,7 @@ let
     ./programs/info.nix
     ./programs/lesspipe.nix
     ./programs/man.nix
+    ./programs/mbsync.nix
     ./programs/mercurial.nix
     ./programs/neovim.nix
     ./programs/newsboat.nix
diff --git a/modules/programs/mbsync.nix b/modules/programs/mbsync.nix
new file mode 100644
index 000000000..f0e6fc1f1
--- /dev/null
+++ b/modules/programs/mbsync.nix
@@ -0,0 +1,241 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  dag = config.lib.dag;
+
+  cfg = config.programs.mbsync;
+
+  # Accounts for which mbsync is enabled.
+  mbsyncAccounts =
+    filter (a: a.mbsync.enable) (attrValues config.accounts.email.accounts);
+
+  genTlsConfig = tls: {
+      SSLType =
+        if !tls.enable          then "None"
+        else if tls.useStartTls then "STARTTLS"
+        else                         "IMAPS";
+    }
+    //
+    optionalAttrs (tls.enable && tls.certificatesFile != null) {
+      CertificateFile = tls.certificatesFile;
+    };
+
+  masterSlaveMapping = {
+    none = "None";
+    imap = "Master";
+    maildir = "Slave";
+    both = "Both";
+  };
+
+  genSection = header: entries:
+    let
+      escapeValue = escape [ "\"" ];
+      genValue = v:
+        if isList v
+        then concatMapStringsSep " " genValue v
+        else "\"${escapeValue v}\"";
+    in
+      ''
+        ${header}
+        ${concatStringsSep "\n"
+          (mapAttrsToList (n: v: "${n} ${genValue v}") entries)}
+      '';
+
+  genAccountConfig = account: with account;
+    if (imap == null || maildir == null)
+    then ""
+    else
+      genSection "IMAPAccount ${name}" (
+        {
+          Host = imap.host;
+          User = userName;
+          PassCmd = toString passwordCommand;
+        }
+        //
+        genTlsConfig imap.tls
+        //
+        optionalAttrs (imap.port != null) { Port = toString imap.port; }
+      )
+      + "\n"
+      + genSection "IMAPStore ${name}-remote" {
+        Account = name;
+      }
+      + "\n"
+      + genSection "MaildirStore ${name}-local" (
+        {
+          Path = "${maildir.absPath}/";
+          Inbox = "${maildir.absPath}/${folders.inbox}";
+          SubFolders = "Verbatim";
+        }
+        //
+        optionalAttrs (mbsync.flatten != null) { Flatten = mbsync.flatten; }
+      )
+      + "\n"
+      + genSection "Channel ${name}" {
+        Master = ":${name}-remote:";
+        Slave = ":${name}-local:";
+        Patterns = mbsync.patterns;
+        Create = masterSlaveMapping.${mbsync.create};
+        Remove = masterSlaveMapping.${mbsync.remove};
+        Expunge = masterSlaveMapping.${mbsync.expunge};
+        SyncState = "*";
+      }
+      + "\n";
+
+  genGroupConfig = name: channels:
+    let
+      genGroupChannel = n: boxes: "Channel ${n}:${concatStringsSep "," boxes}";
+    in
+      concatStringsSep "\n" (
+        [ "Group ${name}" ] ++ mapAttrsToList genGroupChannel channels
+      );
+
+in
+
+{
+  options = {
+    programs.mbsync = {
+      enable = mkEnableOption "mbsync IMAP4 and Maildir mailbox synchronizer";
+
+      package = mkOption {
+        type = types.package;
+        default = pkgs.isync;
+        defaultText = "pkgs.isync";
+        example = literalExample "pkgs.isync";
+        description = "The package to use for the mbsync binary.";
+      };
+
+      groups = mkOption {
+        type = types.attrsOf (types.attrsOf (types.listOf types.str));
+        default = {};
+        example = literalExample ''
+          {
+            inboxes = {
+              account1 = [ "Inbox" ];
+              account2 = [ "Inbox" ];
+            };
+          }
+        '';
+        description = ''
+          Definition of groups.
+        '';
+      };
+
+      extraConfig = mkOption {
+        type = types.lines;
+        default = "";
+        description = ''
+          Extra configuration lines to add to the mbsync configuration.
+        '';
+      };
+    };
+
+    accounts.email.accounts = mkOption {
+      options = [
+        {
+          mbsync = {
+            enable = mkEnableOption "synchronization using mbsync";
+
+            flatten = mkOption {
+              type = types.nullOr types.str;
+              default = null;
+              example = ".";
+              description = ''
+                If set, flattens the hierarchy within the maildir by
+                substituting the canonical hierarchy delimiter
+                <literal>/</literal> with this value.
+              '';
+            };
+
+            create = mkOption {
+              type = types.enum [ "none" "maildir" "imap" "both" ];
+              default = "none";
+              example = "maildir";
+              description = ''
+                Automatically create missing mailboxes within the
+                given mail store.
+              '';
+            };
+
+            remove = mkOption {
+              type = types.enum [ "none" "maildir" "imap" "both" ];
+              default = "none";
+              example = "imap";
+              description = ''
+                Propagate mailbox deletions to the given mail store.
+              '';
+            };
+
+            expunge = mkOption {
+              type = types.enum [ "none" "maildir" "imap" "both" ];
+              default = "none";
+              example = "both";
+              description = ''
+                Permanently remove messages marked for deletion from
+                the given mail store.
+              '';
+            };
+
+            patterns = mkOption {
+              type = types.listOf types.str;
+              default = [ "*" ];
+              description = ''
+                Pattern of mailboxes to synchronize.
+              '';
+            };
+          };
+        }
+      ];
+    };
+  };
+
+  config = mkIf cfg.enable {
+    assertions = [
+      (
+        let
+          badAccounts = filter (a: a.maildir == null) mbsyncAccounts;
+        in
+          {
+            assertion = badAccounts == [];
+            message = "mbsync: Missing maildir configuration for accounts: "
+              + concatMapStringsSep ", " (a: a.name) badAccounts;
+          }
+      )
+
+      (
+        let
+          badAccounts = filter (a: a.imap == null) mbsyncAccounts;
+        in
+          {
+            assertion = badAccounts == [];
+            message = "mbsync: Missing IMAP configuration for accounts: "
+              + concatMapStringsSep ", " (a: a.name) badAccounts;
+          }
+      )
+    ];
+
+    home.packages = [ cfg.package ];
+
+    home.file.".mbsyncrc".text =
+      let
+        accountsConfig = map genAccountConfig mbsyncAccounts;
+        groupsConfig = mapAttrsToList genGroupConfig cfg.groups;
+      in
+        concatStringsSep "\n" (
+          [ "# Generated by Home Manager.\n" ]
+          ++ accountsConfig
+          ++ groupsConfig
+          ++ optional (cfg.extraConfig != "") cfg.extraConfig
+        );
+
+    home.activation.createMaildir =
+      dag.entryBetween [ "linkGeneration" ] [ "writeBoundary" ] ''
+        $DRY_RUN_CMD mkdir -m700 -p $VERBOSE_ARG ${
+          concatMapStringsSep " " (a: a.maildir.absPath) mbsyncAccounts
+        }
+      '';
+  };
+}