Update dependency MailKit to 4.12.0 (#1052)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

src/Directory.Packages.props

@@ -617,7 +617,7 @@
 	</ItemGroup>
 	<!-- 👇 Mail（邮箱 📫） -->
 	<ItemGroup>
-		<PackageVersion Include="MailKit" Version="4.10.0">
+		<PackageVersion Include="MailKit" Version="4.12.0">
 		</PackageVersion>
 	</ItemGroup>
 	<!-- 👇 SourceLink -->