feat: add support for custom Outlook folder search

- Allow searching custom folders by name (e.g., "Projects", "Archive")
- Add recursive folder search through all stores/accounts
- Include Inbox subfolders when searching "All"
- Update parameter descriptions to document custom folder support

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -0,0 +1,36 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Build Commands
+
+```bash
+# Build the project
+dotnet build EmailSearch/EmailSearch.csproj
+
+# Build release version
+dotnet build EmailSearch/EmailSearch.csproj -c Release
+
+# Run the MCP server (connects via stdio)
+dotnet run --project EmailSearch/EmailSearch.csproj
+```
+
+## Architecture
+
+This is an MCP (Model Context Protocol) server that provides Outlook email search capabilities to LLM clients. It runs as a stdio-based server using the Microsoft.Extensions.Hosting pattern.
+
+**Key Components:**
+
+- `Program.cs` - Entry point that configures the MCP server with stdio transport and registers `EmailSearchTools`
+- `EmailSearchTools.cs` - MCP tool implementations decorated with `[McpServerTool]`:
+  - `SearchEmails` - Search emails with filters (keywords, sender, subject, date range, folder, attachments, importance, category, flag status)
+  - `ReadEmail` - Retrieve full email body by subject and date
+- `SearchFilters.cs` - Filter parameter container for email searches
+- `EmailResult.cs` - DTO for search results with factory method `FromMailItem()`
+
+**Dependencies:**
+
+- `ModelContextProtocol` - MCP SDK for .NET
+- `NetOfficeFw.Outlook` - COM interop wrapper for Outlook automation
+
+**Platform:** Windows-only (.NET 9.0-windows) due to Outlook COM dependency

EmailSearch/EmailSearch.csproj

@@ -10,7 +10,7 @@
 
   <ItemGroup>
     <PackageReference Include="ModelContextProtocol" Version="0.1.0-preview.14" />
-    <PackageReference Include="Microsoft.Extensions.Hosting" Version="9.0.0" />
+    <PackageReference Include="Microsoft.Extensions.Hosting" Version="10.0.1" />
     <PackageReference Include="NetOfficeFw.Outlook" Version="1.9.7" />
   </ItemGroup>
 

EmailSearch/EmailSearchTools.cs

@@ -27,7 +27,7 @@ public class EmailSearchTools
         [Description("Number of days back to search (default 365)")] int daysBack = 365,
         [Description("Maximum number of results to return (default 25)")] int maxResults = 25,
         [Description("Number of results to skip for pagination (default 0)")] int offset = 0,
-        [Description("Outlook folder to search: Inbox, SentMail, Drafts, DeletedItems, Junk, or All (default All)")] string folder = "All",
+        [Description("Outlook folder to search: Inbox, SentMail, Drafts, DeletedItems, Junk, All, or any custom folder name (default All)")] string folder = "All",
         [Description("Filter by attachment: 'true' for emails with attachments, 'false' for without, or filename to search")] string? hasAttachment = null,
         [Description("Filter by importance: High, Normal, or Low")] string? importance = null,
         [Description("Filter by category name")] string? category = null,
@@ -79,7 +79,7 @@ public class EmailSearchTools
     public static string ReadEmail(
         [Description("Exact or partial subject line to match")] string subject,
         [Description("Date of the email (supports: yyyy-MM-dd, MM/dd/yyyy, dd/MM/yyyy)")] string date,
-        [Description("Outlook folder: Inbox, SentMail, Drafts, DeletedItems, Junk, or All (default All)")] string folder = "All")
+        [Description("Outlook folder: Inbox, SentMail, Drafts, DeletedItems, Junk, All, or any custom folder name (default All)")] string folder = "All")
     {
         try
         {
@@ -125,6 +125,9 @@ public class EmailSearchTools
         {
             folders.Add(ns.GetDefaultFolder(OlDefaultFolders.olFolderInbox));
             folders.Add(ns.GetDefaultFolder(OlDefaultFolders.olFolderSentMail));
+            // Also search subfolders of Inbox for "All"
+            var inbox = ns.GetDefaultFolder(OlDefaultFolders.olFolderInbox);
+            AddSubfolders(inbox, folders);
         }
         else if (folderMap.TryGetValue(folder, out var olFolder))
         {
@@ -137,10 +140,74 @@ public class EmailSearchTools
                 // Folder may not exist (e.g., Archive on some configurations)
             }
         }
+        else
+        {
+            // Search for custom folder by name
+            var customFolder = FindFolderByName(ns, folder);
+            if (customFolder != null)
+            {
+                folders.Add(customFolder);
+            }
+        }
 
         return folders;
     }
 
+    private static MAPIFolder? FindFolderByName(_NameSpace ns, string folderName)
+    {
+        // Search through all accounts/stores
+        foreach (var store in ns.Stores)
+        {
+            if (store is Store s)
+            {
+                try
+                {
+                    var rootFolder = s.GetRootFolder() as MAPIFolder;
+                    if (rootFolder != null)
+                    {
+                        var found = SearchFolderRecursive(rootFolder, folderName);
+                        if (found != null)
+                            return found;
+                    }
+                }
+                catch
+                {
+                    // Skip stores that can't be accessed
+                }
+            }
+        }
+        return null;
+    }
+
+    private static MAPIFolder? SearchFolderRecursive(MAPIFolder parent, string folderName)
+    {
+        foreach (var subfolder in parent.Folders)
+        {
+            if (subfolder is MAPIFolder folder)
+            {
+                if (folder.Name.Equals(folderName, StringComparison.OrdinalIgnoreCase))
+                    return folder;
+
+                var found = SearchFolderRecursive(folder, folderName);
+                if (found != null)
+                    return found;
+            }
+        }
+        return null;
+    }
+
+    private static void AddSubfolders(MAPIFolder parent, List<MAPIFolder> folders)
+    {
+        foreach (var subfolder in parent.Folders)
+        {
+            if (subfolder is MAPIFolder folder)
+            {
+                folders.Add(folder);
+                AddSubfolders(folder, folders);
+            }
+        }
+    }
+
     private static MailItem? FindEmail(MAPIFolder folder, string subject, DateTime targetDate)
     {
         var items = folder.Items;