Hi,

I recently had a very similar task and after a little digging around came up with the below class to do the job. It hooks into the member save event and should trigger an email at the appropriate point. Hopefully it will prove useful for anyone with the same problem in the future.

Paul

using System.Collections.Generic;
using System.Web;
using Umbraco.Core;
using Umbraco.Core.Models;
using Umbraco.Core.Services;
using Umbraco.Web;

public class MemberEvents : IApplicationEventHandler
{

    private static UmbracoHelper _umbHelper;
    private static UmbracoHelper umbHelper
    {
        get
        {
            if (_umbHelper != null)
                return _umbHelper;

            //Ensure we have an umbraco context
            if (UmbracoContext.Current == null)
                UmbracoContext.EnsureContext(new HttpContextWrapper(HttpContext.Current), ApplicationContext.Current, true);

            _umbHelper = new UmbracoHelper(UmbracoContext.Current);

            return _umbHelper;
        }
    }

    // Register the save members event we need to hook into
    public void OnApplicationInitialized(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
    {
        Umbraco.Core.Services.MemberService.Saving += this.MemberService_Saving;
    }

    // Before a member is saved
    internal void MemberService_Saving(IMemberService sender, Umbraco.Core.Events.SaveEventArgs<IMember> e)
    {
        foreach (IMember member in e.SavedEntities)
        {
            //Member is not approved, dont send an email at all
            if (!member.IsApproved)
                continue;

            //Pull the old approval state from the member service (this is the value before the save has updated the cache)
            bool oldValue = ApplicationContext.Current.Services.MemberService.GetById(member.Id).IsApproved;

            //Member wasn't approved before save but is now
            if (oldValue != member.IsApproved)
            {
                //Code to send email goes here
            }
        }
    }

    public void OnApplicationStarted(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
    {
        // unused
    }

    public void OnApplicationStarting(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
    {
        // unused
    }
}