Signup with email authentication, only 30% are activated?

I have a website which let users to sign up. The signup process including sending "activation email", click link to activate account.

The first two weeks was fine. Out of around 2000 users, 1800 users are activated. After that, the activated users drop drastically, to about 30%. Example: 1000 users signup, only 300 were activated.

At first, I found the problem is because the email could not be reach to ymail, msn and gmail users. (Most of my subscribers are Ymail (yahoo), hotmail/msn(live) and gmail (gmail)). I tried signup using ymail and hotmail, but i didnt get any activation email. I contacted yahoo and msn, eventually my email can go through now.

However, my signup statistic still showing, the activated users are only about 30%, which very confuse me. I contact my hosting company, ask them the whitelist my IP. And they did it.

I need your advice/help on following questions:

• How to check where the problem lies? Is the email not delivered? User receive email but didnt click the activation link?

• I am using php mail funstion. and this is my headers:

  $headers =  'MIME-Version: 1.0' . "\r\n";
  $headers .= 'Content-type: text/html; charset=UTF-8' . "\r\n";
  $headers .= 'From: Admin <admin@domain.com>' . "\r\n";
  $headers .= 'Return-Receipt-To: Bounce <bounce@domain.com>' . "\r\n";
  $headers .= 'Reply-To: Admin <admin@domain.com>' . "\r\n";
  $return_path = "bounce@domain.com";
  

  Is there anything wrong with the headers?

• What can I do to improve my registration/signup activation process?

From serverfault $pageUsers[$entry.posts[0].author].name

• Did you check your mail system logs ? I suggest using a basic script that parses postfix logs to only show rejections in a readable output, you can find it there

  I contact my hosting company, ask them the whitelist my IP. And they did it.

  what do you mean ? Are they relaying your mails ? What do you call 'whitelist' there ? What are they supposed to do ?

  If you have set up the whole mail system by yourself, you are the only one who can act in order to 'whitelist' (I may say 'try to not be blacklisted'...)

  zecrazytux : Oh I see, I first though you were using a dedicated server. If I anderstand well, you don't control anything else that your web applications, no control over the mail system and yo ucan't access the logs... How is your domain managed (I mean in DNS system) ? Check that your hosting company mail servers ip addresses are not blacklisted by DNSRBL lists. It is very hard to control whitelisting/blacklisting when not using a dedicated hosting :(, because you can suffer from other users/clients and you can't control anything
  From zecrazytux

• Put up a 're-request activation' link on the site that will re-send the activation mails. Capture the statistics for the number of people re-requesting the email.

  If it's high, you have a delivery problem. If it's not, you probably have spam bots.

  Alternative approach would be to put a captcha before the email is sent out.

  Also, are you actively capturing and reviewing bounce replies as per the header addresses? If not, you should be doing so. They'll expose a general problem with email sending.

  From Chris Thorpe