Catch-all email servers. What you need to know

3 min read

Catch-All Email Servers

In this article we are going to explain catch-all email servers, why do they exist, why it is a problem for you and how you can find them in your mailing list and build a proper email strategy.

The catch-all email server is a widely used tool that allows an owner to receive all the emails sent to the domain. For example, if your email server domain is then all the letters sent to the email with this domain will reach your server. What does that mean? If someone sends an email to the email which doesn’t exist the letter is still going to be received by your server as there is pointed out domain name.

Why Do The Catch-All Email Servers Exist?

There are mainly two reasons for catch-all email servers to exist:

  • It is used by companies to ensure that no incoming letter is missed (for example, if the sender made a mistake in the email address)
  • Used by email service providers to detect spammers

It is all clear with the first reason, but what about the second one? Well, the thing is ESP companies create catch-all email servers and block all the senders that deliver letters to unexisting addresses. Just because these addresses do not really belong to any person and cannot be used to subscribe on newsletters, so in case someone has sent a letter to such an address he is definitely a spammer.

Types of Catch-All Mailboxes

There are two types of catch-all mailboxes:

  • Pure - these are the ones that were created by ESP and have never been used by the real people. Email service providers share them on websites that sell email bases to define spammers that use such websites and block them.
  • Recycled - these are the most dangerous catch-all mailboxes since they were once used by real people, but were abandoned long time ago. Email Service providers use them to detect spammers.

Catch-All Email Servers

Why Catch-All Domains Are The Problem for You?

If you conduct email marketing campaigns, then any catch-all email domain in your base becomes a huge problem, even if it is not created by the ESP. Here is the list of reasons why you should solve the issues with catch-all emails:

  • They increase the bounce rate that negatively affects your reputation as a sender, ESP`s do not like emails that produce letters with a high bounce rate and your email can be blocked for spam.
  • If you send a letter to the pure catch-all email your domain gets marked as a spammer immediately as ESPs know that the only way you could acquire such email address is by using blackhat email marketing methods.
  • Low opening rate, that is caused by the fact, that no-one really opens email letters that ended up on a catch-all email server. A low opening rate negatively affects your reputation and puts your email campaign at risk.

How to Provide Email Verification for Catch-All Email Servers?

There is no silver bullet to do this safely. All you can do when dealing with the catch-all domains is to get rid of the non-existing or non-actively used emails in your mailing list and build a strategy that decreases the risks of getting a spammer marker for your email domain.

Email Automation

How to Build a Proper Strategy of Dealing with Catch-All Email Servers?

There are several steps for you to take if you want to make sure your mailing list remains safe for your domain:

  • Use a double opt-in subscription - in a such a way you are guaranteed from making mistakes in email address writing and always get real active users in your mailing list.
  • NEVER purchase or exchange mailing lists from unreliable companies or services.
  • Do not send newsletters to the old mailing lists
  • Use advanced subscription forms to prevent getting bots in your mailing lists and always check domains of the email addresses
  • Use suppression lists - a list of emails you cannot send emails on.
  • Customize soft bounce processing. For example, if per one address you got more than 4 soft bounces then delete such address from your mailing list.

How to Find Catch-All Emails in Your Mailing List?

Actually, you do not really need to find such emails - your goal is to find emails that were created by ESPs to catch spammers and emails that are not really used. First of all, never use the mailing lists from the third parties you do not trust. In order to find the emails that harm your sender’s reputation you need to:

  • Analyze the bounce rate - if it is abnormally high for the group of emails you acquired in the specified period you better get rid of those in your mailing list.
  • Analyze delivery mistake reports - all the emails that produce delivery mistakes for any reason should better be deleted.


Catch-all email servers are the big problem for all of those who deal with email marketing. Even if you use only the whitehat methods you are not guaranteed from accidentally sending an email to the catch-all email server. However, there is no need to panic, just use the recommendations above to build the strategy and define broken emails and you are likely to avoid any issues with this problem.

Read more in other useful articles on our blog.

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