namespace Sitecore.Feature.EmailConfiguration.Facets{
[Serializable]
[FacetKey(DefaultFacetKey)]
public class EmailUser:Sitecore.XConnect.Facet
{
    public const string DefaultFacetKey = "EmailUser";
    public string Username { get; set; }
    public string Password { get; set; }
    public EmailUser()
    {

    }
}
}

namespace Sitecore.Feature.EmailConfiguration.Models
    {
    public  class EmailUserModel
    {
        public static XdbModel Model { get; } = EmailUserModel.BuildModel();

        public static XdbModel BuildModel()
        {
            XdbModelBuilder modelBuilder = new XdbModelBuilder("EmailUserModel", new XdbModelVersion(0, 1));

            modelBuilder.ReferenceModel(Sitecore.XConnect.Collection.Model.CollectionModel.Model);
            modelBuilder.DefineFacet<Contact, EmailUser>(EmailUser.DefaultFacetKey);

            return modelBuilder.BuildModel();
        }
    }
}

namespace Sitecore.Feature.EmailConfiguration.Mappers
{
    public class EmailUserFacetMapper : IFacetMapper
    {
        private readonly PreferredEmailFacetMapper mapper;

        public EmailUserFacetMapper(): this(CollectionModel.FacetKeys.AddressList)
        {
        }
        public EmailUserFacetMapper(string facetName)
        {
            Assert.ArgumentNotNull(facetName, nameof(facetName));

            this.FacetName = facetName;
        }

        public string FacetName { get; }

        public MappingResult Map(string facetKey, Facet facet, ContactMappingInfo mappings, string[] data)
        {
            using (EventLog eventLog = new EventLog("Application"))
            {
                eventLog.Source = "Application";
                eventLog.WriteEntry("EmailUserFacetMapperCalled facetKey:" +facetKey+" data"+ string.Join("; ", data));
            }

            if (facetKey != this.FacetName)
            {
                return new NoMatch(facetKey);
            }

            var emailUser = new EmailUser();

            var username = mappings.GetValue("EmailUser_Username", data);
            var password = mappings.GetValue("EmailUser_Password",data);

            if (!string.IsNullOrEmpty(username)) { emailUser.Username = username; }
            if (!string.IsNullOrEmpty(password)) { emailUser.Password = password; }

            return (MappingResult)new FacetMapped(facetKey, (Facet) emailUser);
        }
    }
}

namespace Sitecore.Feature.EmailConfiguration.TokenMaps
{
    public class EmailUserPropertyTokenMap : DefaultRecipientPropertyTokenMap
    {
        protected static readonly MethodInfo GetUsernameValue = typeof(FacetExtensions).GetMethod(nameof(FacetExtensions.GetUsernameValue), new[] { typeof(EmailUser) });
        protected static readonly MethodInfo GetPasswordValue = typeof(FacetExtensions).GetMethod(nameof(FacetExtensions.GetPasswordValue), new[] { typeof(EmailUser) });




        static EmailUserPropertyTokenMap()
        {
            if (TokenBindings == null)
            {
                TokenBindings = new Dictionary<Token, RecipientPropertyTokenBinding>();
            }
            RecipientPropertyTokenBinding usernameTokenBinding = RecipientPropertyTokenBinding.Build<EmailUser>(new Token("username"), null, GetUsernameValue);
            RecipientPropertyTokenBinding passwordTokenBinding = RecipientPropertyTokenBinding.Build<EmailUser>(new Token("password"), null, GetPasswordValue);

            TokenBindings.Add(usernameTokenBinding.Token, usernameTokenBinding);
            TokenBindings.Add(passwordTokenBinding.Token, passwordTokenBinding);
        }
    }
    public static class FacetExtensions
    {
        public static string GetUsernameValue(this EmailUser facet)
        {
            return facet.Username;
        }

        public static string GetPasswordValue(this EmailUser facet)
        {
            return facet.Password;
        }
    }
}

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/" xmlns:set="http://www.sitecore.net/xmlconfig/set">
  <sitecore>
    <exm>
      <dispatchTask type="Sitecore.Feature.EmailConfiguration.DispatchTasks.EmailUserDispatchTask, Sitecore.Feature.EmailConfiguration" patch:instead="*[@type='Sitecore.EmailCampaign.Cm.Dispatch.DispatchTask, Sitecore.EmailCampaign.Cm']">
        <param ref="exm/dispatchFailedTaskPool"/>
        <param desc="recipientValidator" ref="exm/recipientValidator" />
        <param desc="contactService" ref="exm/contactService" />
        <param desc="dataProvider" ref="exm/dataProvider" />
        <param desc="itemUtil" ref="exm/itemUtil" />
        <param desc="eventDataService" ref="exm/eventDataService" />
        <param desc="dispatchManager" ref="exm/dispatchManager" />
        <param desc="emailAddressHistoryManager" ref="exm/emailAddressHistoryManager" />
        <param desc="recipientManagerFactory" ref="exm/recipientManagerFactory" />
        <param desc="sentHistoryManager" ref="exm/sentHistoryManager" />
      </dispatchTask>
    </exm>
    <recipients>
      <recipientPropertyTokenMap type="Sitecore.Feature.EmailConfiguration.TokenMaps.EmailUserPropertyTokenMap, Sitecore.Feature.EmailConfiguration" singleInstance="true" patch:instead="*[@type='Sitecore.Modules.EmailCampaign.Core.Personalization.DefaultRecipientPropertyTokenMap, Sitecore.EmailCampaign']" />
    </recipients>

    <import>
      <facetMappers hint="list:Add">
      <facetMapper type="Sitecore.Feature.EmailConfiguration.Mappers.EmailUserFacetMapper,Sitecore.Feature.EmailConfiguration" />
        </facetMappers>
    </import>
    <settings>
      <setting name="ListManagement.Import.FacetsToMap">
        <set:attribute name="value">Emails|Personal|Addresses|EmailUser</set:attribute>
      </setting>
    </settings>

 <xconnect>
      <runtime type="Sitecore.XConnect.Client.Configuration.RuntimeModelConfiguration,Sitecore.XConnect.Client.Configuration">
        <schemas hint="list:AddModelConfiguration">
              <schema name="EmailUserModel" type="Sitecore.XConnect.Client.Configuration.StaticModelConfiguration,Sitecore.XConnect.Client.Configuration">
                  <param desc="modeltype">Sitecore.Feature.EmailConfiguration.Models.EmailUserModel,Sitecore.Feature.EmailConfiguration</param>
              </schema>
        </schemas>
      </runtime>
    </xconnect>

  </sitecore>
</configuration>