/// <summary>
/// Sets mailbox identifier in email draft.
/// </summary>
/// <param name="activity"><see cref="Activity"/> instance.</param>
/// <param name="emailMessage"><see cref="EmailMessage"/> instance.</param>
protected void SetMailboxInEMD(Entity activity, EmailMessage emailMessage)
{
var helper = ClassFactory.Get <EmailMessageHelper>(
new ConstructorArgument("userConnection", UserConnection));
var headers = emailMessage.HeaderProperties.ToDictionary(pair => pair.Name, pair => pair.Value);
var ticks = ActivityUtils.GetSendDateTicks(UserConnection, activity);
headers["SendDateTicks"] = ticks.ToString();
helper.CreateEmailMessage(activity, Guid.Empty, headers, true);
}