Communications blocked by email service providers

Email service providers (, yandex, gmail etc.) use complex spam-filters to protect their users from spam, these filters determine if your email will be delivered to user“s inbox. If a spam filter suspects a sender in spam, it may block all the future communications of this particular sender.
How to determine if an email service has blocked the communications

  • Check the delivery statistics with domain details after each campaign

Report Delivery – Domains shows the delivery rate for popular email services. If a communication was blocked by or you will see a rapid delivery drop for the domain.

  • Register with Postmaster and Postoffice services

Email service providers offer free service for senders to control their communications delivery: Postmaster for (sender is registered by DKIM), Postoffice for (by senders email). There you can check delivery logs, complaints, etc.
Possible reasons for being blocked

It is impossible to determine the reasons for being blocked by spam-filters in each case, due to security settings, the ways the filters work are not published.
There are few common types:

  • Email Database

Email service providers filters analize the recepients database. Several problems occur:
– Database contains honeypots. These are special emails that email service providers publish somewhere on the internet for public access. Through parsers (special programs to collect emails from web-sites) a honeypot is collected into spam-bases, and, sometimes, into bases of companies that want to expand their subscribers databases. Presence of a honeypot in the database suggests that at least some part was collected illegally.
– The database contains 3% of not existing emails. This is also one of the reasons of a spam base. Spammers generate databases using the wors combinations with popular domain names(for example - ivanov + =, targeting the existing emails. In such a database a major part of emails does not exist. The database of an honest sender cannot contain a huge number of emails that do not exist.
Note: Sendsay determines if an email exists by the first communication to the given email. If an email does not exist, it will be excluded from all the future campaigns.

  • Recepients responses

Email services have special button «This is spam» or «Mark as spam», using which a user can complain about email spam. If one user complaints, nothing bad happens. Sometimes, people who are too lazy to find an opt-out link at the end of the email. Problems start when more that 1% of subscribers press these button. For a spam-filter this is a sign that a user broke the rules of added illegally parsed emails, or, perhaps, added something to the content that caused resentment among subscribers. The campaign may be delaysed or even block all the future communications of the sender.

  • Email content

Filters accumulate information about signs of spam: specific words (make money on the internet, easy money, passive income, 100% profitable, etc.) formatting (red letters, upper case, cursive, bold), scripts, sispicious attachments, absence of text (a whole email is an image), etc. Filters determine the set of criteria and may forward your communication into «spambox» or even decline your email.

  • Sender's reputation.

The сrucial factor for being marked as spam. If an IP-address from which the communication was executed was listed as spammer, the probability for being marked as spam is high. A sender's reputation consists of a number of factors and may be higher or lower depending on the results of previous campaigns and recipients responses.
What to do if an email service provider blocked the campaign
If your campaign was declined as spam or all of your communication are blocked by an email service provider, follow the recommendations:
Adjust your subscribers management routine:

  • Set-up Double Opt In.
  • Remove non-existing emails.
  • Work only with double opt-ins, only those, whose subscription you can prove. .
  • Remove inactive subscribers, who did not open your emails withing the last 3-6 months, or send them an invitation to re-subscribe, remove them from automated campaigns and reduce the quantity of emails you send to them.
  • If your automated campaigns have poor performance, stop them for some time.

Contact the support of the service which blocked your campaigns and ask them to explain the reasons for being marked as spam to make the required corrections. MailRu and Yandex respond within a few days.

When you get the support response, make all the required adjustments. If you ignore them, next time they may not respond.
If your campaign was blocked by Gmail, make the proper adjustments and wait. Normally it re-sets the sender's reputation within 3 weeks. If you removed the reason for being marked as spam, your letters will start coming through.
If you cannot solve the problem on your own, we recommend you to contact Sendsay support.

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