ListMailboxWindow.axaml

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d" d:DesignWidth="600" d:DesignHeight="400"
        x:Class="PoopmailGui.ListMailboxWindow"
        Title="Mailboxes"
        Width="600"
        Height="400"
        TransparencyLevelHint="AcrylicBlur"
        Background="Transparent"
        ExtendClientAreaToDecorationsHint="True">
        <StackPanel Margin="50" Spacing="5">
                <TextBlock Width="200" TextAlignment="Center">Your mailboxes</TextBlock>
                <ListBox Name="ListMailboxes" Height="250" Width="550"></ListBox>
                <Button Width="300" Height="30" HorizontalAlignment="Center" Click="Button_OnClick">
                        <TextBlock TextAlignment="Center">Create</TextBlock>
                </Button>
                <Button Width="100" Height="30" HorizontalAlignment="Center" Click="ButtonOpen_OnClick">
                        <TextBlock TextAlignment="Center">Open</TextBlock>
                </Button>
        </StackPanel>
</Window>