While you are building up your sender reputation by sending campaigns to your audience, it is normal for some of the emails to not make it to the inbox, for a variety of reasons. Here are the top four reasons that emails get blocks and some ways to help resolve or prevent them.

1. Unauthenticated email

Depending on how a receiving server is configured, it will use various methods to determine whether an email comes from:

• The server that it claims sent it
• The email address that it claims sent it
• The domain that it claims sent it
• That the server has been authorized to send on behalf of that email address / domain

If the information above is unaligned, inconsistent, or fraudulent, then the receiving server is more likely to view the email as a security risk. Emails that are viewed as a security risk are typically either rejected completely or sent directly to spam / junk.

Set up DKIM and DMARC authentication; they create alignment and most inbox providers require them now. Never use a freemail address as your sender email address. Before you send your first campaign, be sure you have followed these deliverability best practices.

2. Spammy content

The content of your email can result in a receiving server sending it to the spam folder. Spam filters look at an email as a whole, with thresholds set for certain criteria. If a threshold is exceeded, the email gets marked as spam. Here are some examples of things that can cause an email to be caught by spam filters:

• An entire email composed of capital letters
• Frequent or random capitalization
• Excessive punctuation, especially “$” and “!”
• Strange spacing or excessive amounts of blank space
• Poor spelling
• Frequent variations in text color and size
• Scam-like subject lines

Always adhere to our Anti-Spam Policy which states that emails which contain unbelievable claims about earning money fast, free products / services, adult content, gambling, prizes, and pharmaceuticals are high risk for being marked as spam and are therefore all prohibited. For more information, check out our permission-based list examples.

3. Blocks by an inbox provider

Inbox providers consider every spam complaint to be an official complaint from their customers. This means that if enough recipients mark your email as spam, the inbox provider may respond by blocking future emails from you.

Stay informed about the different types of blocklists that inbox providers use. Additionally, we monitor spam complaints made against every email you send. If complaints about a single email exceed industry thresholds — anything above .01% — your account could be suspended.

4. Custom spam filters

Most major inbox providers use “smart” filters to detect unwanted email, meaning the filter rules change based on past emails, who sent them, and how the recipient interacted with them. Different recipients can have different filters, which means that your email may land in the inbox of one subscriber and in the spam folder of another.

Additional spam filters or rules may have been set up by a company’s IT department or by individual recipients. For example, a person who has decided they want to unclutter their work email inbox could set up a filter to send any email that has the word “sale” in it to their spam folder.

One way to address this is to ask your subscribers to add your email address or domain to their safe sender list, address book, or contacts. Usually, the best time to do this is in your introductory email.