private void copyToClipboard_Click(object sender, EventArgs e)
{
StringBuilder sbAllServers = new StringBuilder();
foreach (ListViewItem item in listMailServers.SelectedItems)
{
if (sbAllServers.Length > 0)
sbAllServers.AppendLine();
sbAllServers.Append(item.Text);
}
if (sbAllServers.Length > 0)
Clipboard.SetText(sbAllServers.ToString());
}