The problem of users not receiving their activation emails is a common one, and especially annoying if you have a new business or product and are trying hard to grow your userbase. Fortunately, the problem is well documented but a clear solution to the problem remains to be seen. It’s another case of throw as many things at the wall as you can and hope that something sticks.
If you have this problem, there are a couple of things you can try aside from simply telling your users to check their junk mail folders (which you should be doing on sign-up anyway).
Reverse DNS Setup
The first thing you should check to see is if your web host has what’s called “reverse DNS” setup on your server. For example, AOL will not accept emails from domains that do not have reverse DNS setup. Reverse DNS basically lets computer networks resolve a domain name from an IP address, hence making it easier to identify and therefore is better for security. Most web hosts should have this setup these days, but you might want to check just in case.
Unique Email Text
Another possible and non technical solution is to have a unique email message. If it’s your standard “Hello User, Welcome to ####…” message, and you’re sending out quite a few of them, then it’s possible that your emails or your domain will be picked up by spam filters and thrown into a users junk mail.
Don’t be spammy
Don’t send out loads of messages that could be considered spam. For more reasons than one, sending out too many emails is another way to get your mail thrown into the spam folder. You also don’t want your users unsubscribing. I know I hate nothing more than a website that thinks I’ll buy more products if they email me every week, or even every day.
Lastly, check to see if you’re blacklisted – and if you are, request you be removed. All major email providers have a system where you can request to check whether you’re emails are being put into a spam folder or being blocked altogether. I sent a message to Yahoo a while back and you do have to wait a while for the message to reach a human and you get a response, but they do usually respond. Apparently Yahoo rarely outright blocks emails, but again, it’s worth checking. More information about Yahoo email problems.