12 August 2019

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Tips & Tricks

Articles to give you more insight into newsletter marketing

Why Your Emails Get Blocked or Filtered?

Why Your Emails Get Blocked or Filtered?

It often happens that legitimate emails are being blocked or moved to the Junk folder by ISPs. Whatever the cause of the email blocking is, you can take it under your control and adjust your email program to overcome the ISP email blocking challenges in your future campaigns. After you understand why ISPs block some emails and how to avoid the problems, you will be able to improve your email deliverability and increase your email open rate.

So, why do emails get blocked or filtered?

As you probably guess the main reason why the emails are filtered is spammy looking content. You will absolutely recognize spam emails at first sight: unknown email address in the From field, misspelled Subject, Subject lines written in ALL CAPS, large and often bold font size, pure promotional and sales content.

Furthermore, have you ever paid attention to the links you use in your emails? You may think why you should care about the links if they are from your own domain. I thought the same until the recent time when I discovered that the links may be a cause of email blocking. If your email message contains links from blocked domains, you have a “chance” to get it filtered or blocked.

Here is a live example from my own experience.

I registered the glockeasymail.com domain 2 years ago but didn’t use it until the recent time. There was only an open source directory link exchange script installed. Some time ago I received an email from PayPal telling that glockeasymail.com was probably hacked and used by spammers to send their PayPal fishing emails. I addressed this issue immediately, removed a hacked directory link exchange script from the site and removed all the scripts uploaded by scammers. It seemed the problem was solved. In fact, it wasn’t.

A few weeks ago I sent an email campaign to my customers. The email contained a link from the glockeasymail.com domain. The majority of emails were sent successfully. As always, I ran the Bounce Handler in EasyMail7 to process bounces. I found that a couple of dozens of emails were blocked by Barracuda and FortiGuard spam filters and returned. The reason was “Spam Content”. That was strange because the email didn’t have any signs of spam. I thought the problem might be in the message format (I sent a HTML email). I changed the message format to plain text and re-sent the email to those customers who didn’t get it. No success. The emails were filtered as spam again. I decided to send a short message to those customers asking them to provide me with a different email address. The short email didn’t contain any links and was delivered successfully. This made me think that the problem might be in the URL I included into my original message and, in particular, in the domain the URL was from. As the domain was used by spammers some time, it may be blacklisted and that’s why some filters block the email as spam.

Keeping this in mind I replaced the original link with a redirect link from our main glocksoft.com domain and re-sent the message. This time the emails passed through the filters and reached the recipients. So, if you find your emails blocked by the spam filters, it may be because of a domain name you use in the message content. A quick solution is to use a redirect method like I did. In the perspective you’ll need to contact the ISPs or spam filters developers to solve the problem with your domain block.

Talking about links in the email body, not only the domain may be a cause of the email blocking or filtering. After analyzing bounced emails I discovered that some anti-spam filters didn’t like the recipient’s email address embedded into the URL. So, if you insert the recipient’s email into the unsubscribe link, or into any other link, keep in mind that this may affect the email deliverability in some cases.

Besides spammy looking email content, there are some other reasons for the ISPs email blocking or filtering such as too many spam complaints, too many invalid addresses on the list, and technical sending issues.

1. Too Many Spam Complaints

Spam complaints hurt your sender’s reputation and, consequently, email deliverability, in great extent. Your sender’s reputation is the first thing the ISP takes into consideration when filtering the emails. Don’t panic if somebody flags your email as spam. Many email marketers receive spam complaints. It’s not a disaster but a sign for you that not everything is fine in your email program. You should address this issue as soon as possible. Here is what you can do:

  • Subscribe to feedback loops from ISPs to be notified when recipients click Spam button on your email.
  • Remove the email addresses of the recipients who sent a spam complaint from your list immediately. Or, at least add them to the exclusion list if you have one in order not to email them anymore.
  • Review your opt-out process and make sure it works. Probably your opt-out procedure is not clear and it’s easier to click “Report Spam” button for some recipients rather than unsubscribe from your mailings.
  • Check your message to ensure that it matches the subscribers’ expectations. If you allow people choose the email format, frequency, content (news, tips, offers, etc.), be sure to follow the subscriber’s preferences.

2. Too Many Invalid Email Addresses

Repeatedly sending messages to invalid email addresses defines you as a spammer and leads to email deliverability challenges. Take care about your email list hygiene and follow these simple rules:

  • Use confirmed subscription method. Single opt-in is good but double opt-in is better. Confirmed subscription requests are the best way to protect against misspelt email addresses and wrong subscriptions.
  • Verify your email list for validity. It’s recommended to check your list for invalid, undeliverable email addresses before your first email campaign. After the email is sent, use the Bounce Handler in EasyMail7 to check your mailbox for bounced emails and remove bounces from your list.
  • Manage unsubscribe requests. People can change their interests, or discontinue using your products so it’s normal when someone unsubscribes from your list. Deal with unsubscribe requests immediately and remove those recipients from your list. It’s even better if you could send them a short confirmation that they were successfully unsubscribed.

3. Technical Sending Issues

Some technical issues such as incorrectly formatted message headers, no reverse DNS, PTR records setup, or authentication errors can lead to email delivery challenges and can cause the emails being filtered or blocked by ISPs. They seem to be serious problems but in fact they are easy to correct. You just need to contact your IT staff, or your server administrator, or your hosting service, or your ISP and notify them about the problem you encountered. Generally, it doesn’t take much time to correct the issue. Here you can read more about how to deal with technical sending issues and get your emails delivered.

How to Find out If Your Email is Delivered to the Inbox, or Spam Folder, or Blocked

The easiest way to determine how your email is treated by different Internet providers is to run an Inbox placement and spam filtering test before sending a real email campaign. The test will show how your message is delivered with major Internet providers around the world and whether it is placed to the Inbox, spam folder or blocked before reaching the recipient’s mailbox.

EasyMail7 Inbox Placement and Spam Filters Report provides this valuable information so you have confidence that your email is reaching your customer. Plus you will see in which Gmail tab your message is delivered to.


Check your mail server’s IP address against DNS based blacklists every few email campaigns. You can use the G-Lock Apps spam testing tools to see your inbox placement, spam scores, authentication issues, daily blacklist monitoring to check if your server’s IP address is blacklisted and get summary email alerts if any problems are detected.

How to Discover Why Your Email is Filtered to the Junk or Bulk Folder

If you find your email to constantly end up in the Junk or Bulk email folder, you can do this simple test to find out the reason of the email filtering.

First of all, pay attention to the links you include into the email. Remove all the links and send the test. Check the report. If the email is placed to the Inbox, the problem is in some URL (or even domain) you used in the email. Consider removing the problem URLs/domains or replace them with different URLs/domains.

If the email sent without URLs is still delivered to the Junk folder, the problem may be in the whole email content. Send an email with a single word “Test” and check how it is placed. If it arrives into the Inbox, the problem is in your email content. Consider revising it.

If the test email with a single word is still moved to the Junk folder, the problem is most likely in your mail server’s IP address which has a poor sender reputation and/or misses proper sender authentication records. In this case whatever email you send, it will be moved to the Junk folder. Consider using a different mail server to send the emails to your recipients.

Well, now you get the idea why the ISPs may block the emails and what to do to pass through the filters. But what if you’re already blocked and your emails don’t reach certain subscribers?

You should contact the ISPs which block the majority of your emails and try to remove your IP address from the block. First, you should review your delivery reports to find out which ISPs blocked your email and why. Then go to the ISP website and read how to resolve the IP block issue. You may need to fill in a form, or send a removal request via email, or call them. At any case, provide the ISP with all the necessary information. If you send the emails through an ISP or e-mail service provider (ESP), you may need to ask someone from their staff to resolve the issue with the IP block for you.

Test Your Deliverability and Spam Score

Within minutes, GlockApps will show you where your email is placed at different ISPs.

At Gmail, you’ll see whether your email lands in the Primary, Promotions, Social tab in the Inbox or in the Spam folder.

Plus, GlockApps comprehensive test checks your email for

  • risky content;
  • authentication problems; 
  • blacklisting issues.

…and provides feedback for common ISP and corporate filters.

Read through your report and note what score you received for each spam filter. If a spam filter did not pass we’ll explain what’s causing the issue.

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