Update to the Zivver SMTP-server

Introduction

Friday, August 28, Zivver implemented an update to the Zivver SMTP server which is used for Zivver Mail Submission, Zivver Plug-in Relay and Zivver SMTP Relay. Following this update, recipients of the message are processed in accordance with the internet standards regarding SMTP (namely RFC5321 and RFC5322). In some cases, this update unexpectedly leads to a problem, which results in a message being delivered to a nonexistent recipient. In this article you can read how you can test whether this problem occurs in your organization and how to implement the workaround.

How do I know if this problem affects my organization?

Sometimes Zivver cannot deliver a Zivver message to a recipient. For example, this can happen because the email address does not exist or because the receiving mail server rejects the message. In such cases, Zivver sends a notification (so-called bounce message) to the sender of the message, stating that the message could not be delivered to the recipient.

The first signal that shows this problem may be affecting your organization is that your organization is receiving a lot of bounce messages. Use the method below to check for this:

Does your organization mail securely with Zivver from an application?

Follow the steps below:

  1. Determine from which applications your organization sends securely with Zivver.
  2. Determine from which email addresses are e-mails securely sent from these applications.
  3. Check the mailboxes of these email addresses to see if they are receiving multiple bounce messages.
  4. Determine whether the outgoing messages from these applications are relayed by the mail server to the Zivver SMTP server.
  5. Determine whether these outgoing messages are forwarded by the mail server to a non-existent recipient.

This setup with a non-existent recipient may be necessary to eventually deliver the message to the Zivver SMTP server.

In that case, the mail server places this nonexistent recipient (before the redirection) prominently on the “envelope” as the recipient of the message. The original recipients (To, CC) are on the letter in the envelope. However, the Zivver SMTP server only looks at the recipients on the envelope after the update. This means that the Zivver message is addressed to the non-existent recipients. In that case, implement the workaround as described below.

Does your organization e-mail safely with Zivver from Outlook and is Zivver Plug-in Relay implemented?

  1. Check whether Zivver Plug-in Relay has been implemented on the basis of this manual.
  2. Check the mailboxes to see if they are receiving multiple bounce messages.

The implementation of Zivver Plug-in Relay within Exchange on-premise requires that a sent Zivver message be redirected to a nonexistent recipient.

In that case, Exchange on-premise places this non-existent recipient (prior to the redirection) prominently on the “envelope” as the recipient of the message. The original recipients (To, CC) are on the letter in the envelope. However, the Zivver SMTP server only looks at the recipients on the envelope after the update. This means that the Zivver message is addressed to the non-existent recipient. In that case, implement the workaround as described below.

Implement the workaround

To avoid the above problems, a workaround is available, with which you can indicate that the Zivver SMTP server should ignore the recipients on the “envelope”. Instead, the Zivver SMTP server is told to look for the recipients on the letter in the envelope. You enable this option by including the following mail header in the message:

X-Zivver-Ignore-Smtp-Recipients: true

When the Zivver SMTP server reads this header, the message is sent to the recipients on the letter in the envelope. This prevents the Zivver message from being delivered to the non-existent recipient.

Zivver recommends that when using the Zivver SMTP server to regularly check that no bounce messages have arrived. A bounce message can occur if the recipient does not exist, but also if a problem has arisen during the delivery of the Zivver message. Zivver continuously monitors across the entire Zivver platform whether the number of bounces remains low and meets our requirements.

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