build: improve OpenSSL find on Windows + disable mailio by default

- USE_MAILIO_IMAP=OFF by default (avoids broken thirdparty/boost)
- OpenSSL find with Windows-specific warning
- Native ImapSynchronizer works without mailio
- PrintSupport added for printing

CMakeLists.txt

@@ -21,7 +21,20 @@ if (USE_MAILIO_IMAP)
     find_package(mailio REQUIRED CONFIG)
 endif()
 
-find_package(Qt6 COMPONENTS Core Gui Widgets Network Sql Test Concurrent REQUIRED)
+# Find OpenSSL for S/MIME support (optional on some platforms)
+find_package(OpenSSL QUIET)
+if (OPENSSL_FOUND)
+    message(STATUS "OpenSSL found: ${OPENSSL_VERSION}")
+    add_compile_definitions(OPENSSL_FOUND)
+else()
+    if (WIN32)
+        message(WARNING "OpenSSL not found - S/MIME support disabled. Install OpenSSL and set OPENSSL_ROOT_DIR to enable.")
+    else()
+        message(WARNING "OpenSSL not found - S/MIME support disabled")
+    endif()
+endif()
+
+find_package(Qt6 COMPONENTS Core Gui Widgets Network Sql Test Concurrent PrintSupport REQUIRED)
 
 set(CMAKE_AUTOMOC ON)
 set(CMAKE_AUTOUIC ON)