3.8.4

## What's Changed
* chore(deps): update xunit-dotnet monorepo by @renovate in https://github.com/rnwood/smtp4dev/pull/1705
* chore(deps): update dependency microsoft.net.test.sdk to v17 by @renovate in https://github.com/rnwood/smtp4dev/pull/1707
* chore(deps): update dependency coverlet.collector to v6 by @renovate in https://github.com/rnwood/smtp4dev/pull/1706
* Fix(smtp): No element in sequence if user cannot be found - Resolves #1708 by @rnwood in https://github.com/rnwood/smtp4dev/pull/1712


**Full Changelog**: https://github.com/rnwood/smtp4dev/compare/3.8.3...3.8.4

[See full installation instructions and options](https://github.com/rnwood/smtp4dev/wiki/Installation)

File Name | Description
-- | --
[Docker rnwood/smtp4dev:3.8.4](https://hub.docker.com/r/rnwood/smtp4dev/tags?page=&page_size=&ordering=&name=3.8.4) | Docker image (Linux and Windows)
[.NET tool Rnwood.Smtp4dev 3.8.4](https://www.nuget.org/packages/Rnwood.Smtp4dev/3.8.4) | .NET tool
[Rnwood.Smtp4dev-win-x64-3.8.4.zip](../../releases/download/3.8.4/Rnwood.Smtp4dev-win-x64-3.8.4.zip) | Windows x64 binary standalone - Server edition
[Rnwood.Smtp4dev.Desktop-win-x64-3.8.4.zip](../../releases/download/3.8.4/Rnwood.Smtp4dev.Desktop-win-x64-3.8.4.zip) | Windows x64 binary standalone - Desktop app edition.
[Rnwood.Smtp4dev-win-arm64-3.8.4.zip](../../releases/download/3.8.4/Rnwood.Smtp4dev-win-arm64-3.8.4.zip) | Windows ARM 62-bit binary standalone
[Rnwood.Smtp4dev-linux-x64-3.8.4.zip](../../releases/download/3.8.4/Rnwood.Smtp4dev-linux-x64-3.8.4.zip) | Linux x64 (Intel 64 bit) binary standalone
[Rnwood.Smtp4dev-linux-musl-x64-3.8.4.zip](../../releases/download/3.8.4/Rnwood.Smtp4dev-linux-musl-x64-3.8.4.zip) | Linux MUSL x64 binary standalone for Linux distros using MUSL libc
[Rnwood.Smtp4dev-noruntime-3.8.4.zip](../../releases/download/3.8.4/Rnwood.Smtp4dev-noruntime-3.8.4.zip) | Architecture independent version. Should run on any platform where the .NET 8.0 (or greater) runtime is installed