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Important information about blocked e-mail addresses - status "mailjet: preblocked

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Sweap uses the e-mail provider Mailjet to send the e-mails in order to be able to guarantee excellent performance for a "mass mailing". Due to the interconnection of Mailjet, it can happen that e-mails sent from Sweap are provided with the status "mailjet: preblocked" by Mailjet and cannot be sent.

Why are emails blocked by Mailjet?

Mailjet has set itself the goal of protecting the shipping reputation of its customers (which also includes Sweap). It is irrelevant whether the dispatch was made by you or another Mailjet customer.

Sending reputation: If an e-mail is repeatedly sent to a non-existent e-mail address, a hard bounce is repeatedly generated. These generated bounces affect the reputation of the sender and can lead to the recipient finally blocking the sender (originator).


You have stored an e-mail address in the guest list in your Sweap account that has already been addressed by you or by other Mailjet customers. If a so-called hard bounce occurs, which was caused either by the recipient (e.g. e-mail address inactive) or by the sender (e.g. high SPAM probability), this address is automatically pre-blocked by Mailjet and provided with the status "mailjet: pre-blocked". It is irrelevant whether this hard bounce was caused by you or another Mailjet sender. As soon as a hard bounce occurs, Mailjet automatically activates preblocking. This preblocking has the purpose of protecting your email reputation and proactively preventing another hard bounce.

You can find more information here:

Mailjet - Why do I have blocked emails?

What happens in the event of a blockage?

If an e-mail address has the status "mailjet: preblocked", Mailjet will not send this e-mail. Mailjet will also prevent any further attempts to send the email.

ATTENTION: If the reason for the hard bounce (high SPAM probability, recipient address inactive, e-mail address incorrect, etc.) has not been remedied, resending (after removing the preblocking) will result in a hard bounce and thus renewed preblocking.

Where can I see which email addresses are currently blocked?

To do this, go to the "E-mail addresses" menu in the account overview on the left. To find out which addresses have been blocked by Mailjet, select the filter Hard Bounce in the column "Bounce Status" and enter mailjet in the column "Bounce Reason".

How do I go about removing blockages?

  1. First of all, we would like to ask you to check whether the blocked e-mail address is correct (the possibility of incorrect spelling etc. can be excluded).
  2. Please send us the e-mail addresses for which the blocking must be removed in writing to We are already working on this, so that you can send us the data directly from your Sweap account in the future.
  3. Sweap will pass the data on to Mailjet in order to have the block removed as quickly as possible. As soon as this has been done, Sweap will inform you and delete the reason for the bounce in your overview. Note: The status is only updated in the menu "E-mail addresses". In the e-mail log area, the status is only updated as soon as a new dispatch is started.
  4. After the block has been removed, the e-mail can be sent again.

How can I prevent preblocking in the future?

  1. To prevent blocking in the future, Mailjet can give your domain a no-block option.
  2. You write an email to with the request to activate the no-block option for the domain [your domain].
  3. Sweap then creates a ticket at Mailjet and your domain owner must also send an e-mail to Mailjet confirming the no-block option. For this, Sweap will provide you with Mailjet's email address separately.
  4. As soon as the option has been activated, we will inform you.
Please note that the pre-blocking option is there to protect the email server from too many bounces from Mailjet. Without pre-blocking, it is theoretically possible for someone to exploit this no-block and "bombard" the recipient domain/server with hard bounces to crash it. For this reason, Mailjet does not generally recommend this option.

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