I have been getting this question a lot recently. To be totally honest, sometimes I feel like the grinch stealing Christmas when I give people the answer. Especially if you're a web designer or developer who is trying to make a client happy.
But honesty is the best policy. Right?
So let's get down to the basic honest truth.............
So how does an email end up in the spam folder? Once the email leaves the server it begins to transverse the internet. As it does this, it travels through individual ISP's who have their own set of spam filters, then it travels through the spam filters that each email exchange (Gmail, Outlook etc) have. Then you have to deal with the individual email client's spam filters. Do you see where I'm going?
But it get's worse. The majority of wordpress websites are on shared hosting. How many site are on shared hosting? A lot! It just takes one of those site to get put on a spam list, then all of the sites associated with that IP address are banned and no emails get through. That's why I tell everyone who is serious, get your own designated IP address for your site. But that doesn't even solve it. In the last few years 13 out of the 15 ip addresses I obtained for clients were already black listed by AT&T. So I had to go through the process of removing them from the blacklist. Not hard, but takes time.
It's not an issue that's just you, it involves everyone, including me. I periodically go through my personal spam folder, because I've found that emails that I have signed up for, (For example: Wordpress Newsletters, Microsoft, Major Stores, etc) somehow end up going into my spam folder. Although I've received them for years, someone changed a setting of a spam filter somewhere along the line, or I accidentally marked the email as spam, so they now go into my spam folder.
I understand that this can be a hard pill to swallow. Especially if you starting out on your own or trying to please a client. But', its the honest truth.
What am I doing about it? I'm currently working on three separate plugins for DOIFD that will work with Mandrill, Sendgrid & Amazon SES for the verification email. But just be aware, these service will help tremendously, but still aren't 100%. .
In the mean time, when dealing with the problem of the spam folder, a good place to start is with the with Gmail's Bulk Senders Guidelines, although DOIFD is not sending emails in bulk there are things you can do on a server level that will help. Just keep in mind, this is just for Gmail. All the others have their own guidelines.
Mailchimp also has a good article explaining Spam.
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