Emails Flagged as Spam

“When I send a newsletter few or many subscribers get it as spam/unsolicited email. How can I solve this problem?”

The correct question is: what caused my emails to be marked as spam (by some email providers)?

There are many factors playing in this story: the originating mail servers, the newsletter content, the spam filters on the recipient side or sometime in the sending mail system. It’s not always easy to find the final answer.

You can read even more:

Emails sent by blogs don’t use trusted mail servers

Many providers offering a web space where to install a WordPress blog, even offer a ready to use mail service (used by WordPress, for example, to send emails when a user registers). But at the end, a mail service is nothing else than a server (computer) which sends emails. That server is not necessarily the server which hosts the blog.

Providers don’t care too much of those mail servers and they can be added to black lists. A black list is a list of (mail) servers which should be considered unreliable. If the server you indirectly use to send emails is in a black list, and that black list is used to check the emails quality by the email providers of your subscribers, your message can be marked as spam.

Example: your mail server is in the black list A but not in the black list B and you have two subscribers on different providers, Gmail and Yahoo. Let assume that Yahoo uses the black list A and Gmail the black list B.

Yahoo will probably mark your email as spam but Gmail doesn’t. That explains why not all messages are considered unsolicited email and why all messages to Yahoo mailboxes are.

Black lists can be checked on

If you have your own server

If you have your own server with your own IP address, and you use it to send email, ask the support to create the SPF records for your domain. That topic is a little complex and needs a system administrator but in few words is a way to officially say: the server X is authorized to send email for the domain “”.

A clean list matter

If you send email to a dirty list containing not confirmed email address or spam spy addresses, you can compromise the server/newsletter spam score. Always use the double opt in and if you import addresses from another source be sure they are confirmed.

If you migrate a list from one server to your newsletter (for example Feedburner) be sure to send a first message to the subscriber advising about that change and offering a way to unsubscribe. If users starts to mark the emails as spam your reputation will fall down and the subsequent emails can be marked automatically as spam.

Email content matters

The black lists are only a part of the story. There are systems which evaluate the email content (and the number of email sent with the same content) to decide if a good email server is anyway sending something that seems spam.

Those filters can be installed even on your provider side, so while the email seems to be sent out successfully, it never reach the final recipient. It’s sometime called “mail dropping”.

A story. Few months ago a Newsletter user claimed the test emails were correctly delivered while the regular newsletter were not.

After a number of tests, I created a simple newsletter without links and images: it was delivered. Then I started to add the original links and images, and it was correctly delivered. Until I added a top banner which was hosted on a another domain: the emails wasn’t delivered anymore.

Finally we discovered the hosting provider had some filters on email content which dropped emails containing references to images on different domain that the one hosted. Moving that banner on the hosted web space solved the question.

The story is an example of email spam rating: there are filters that decide if the email content is or not spam. As for the black list every provider on the sending and on the receiving side can have their own filters and so you can experience a different behavior.

No all providers are bad and if they give you an SMTP…

I used many providers for my and experienced different attention about their mail server. There are provider completely ignoring the black list and letting their server to be listed, and other caring about this problem and trying to keep the server clean.

Some provider other that the web space give even a mail server with which one can create mailboxes for his business. Sine that mailboxes requires an incoming and an outgoing mail server, the provider should give the parameter to connect your mail client (for example Outlook or Thunderbird) to the SMTP service (the outgoing server).

Those parameter should work even with Newsletter and those servers are usually much better than the ones available by default to your blog. Try them!

Here a more extended article on using your provider SMTP.

External mail servers

If you really need quality, you can even use external mail service to send emails. Some example of services I used are SendGrid, MailJet and Mandrill. You can use them directly with Newsletter setting their SMTP values on main configuration, or using the Newsletter extensions so you can even enable the bounce checking and the API connection method (which by pass some provider external connection blocks – GoDaddy to cite one).