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Encryption Gateway
Introduction
This guide explains when to use Zivver Encryption Gateway and how to set it up.
Zivver Encryption Gateway uses Microsoft Exchange (Server and Online) mail flow rules to implement secure delivery of selected messages. It is also possible to connect an external application directly to the Zivver SMTP Gateway to implement secure delivery of all messages sent from that application.
Implement Encryption Gateway within your organization to securely deliver messages when:
- A specific (word in the) subject is used.
- When your organization wants to allow employees to be able to send a secure message, independent of the device and/or application that they are using for creating the message. For example a Mail App on a mobile device for which there is currently no Zivver client available.
- A message and/or an attachment has a certain Sensitivity Label applied.
- When your organization uses Microsoft’s Sensitivity Labels so that employees easily stay compliant with your policies of information protection.
- A specific email address is used as the Sender.
- When a specific application automatically sends out messages that need to be delivered securely and a fixed email address is used as the Sender (From:).
- A specific application is used to send out messages.
- When all messages from a specific application needs to be deliverd securely and are send directly from the application.
Requirements
To implement Encryption Gateway your organization must meet these requirements.
- Microsoft Exchange (Server or Online) is used when messages need to be securely delivered when:
- A specific (word in the) subject is used.
- A specific email address is used as the Sender.
- Microsoft Exchange Online (Office 365) is used when messages need to be securely delivered when there’s a Sensitivity Label applied.
- Microsoft’s Sensitivity Labels are only available in Office 365 with certain Microsoft licenses.
- You do not use a Secure Email Gateway (SEG).
- Exceptions are:
- With that SEG, you can configure a connection with
- Host name: smtp.zivver.com
- Port: 25 or 587
- Security: TLS 1.2 with STARTTLS
- This connection is authenticated by either:
- SMTP credentials.
- SPF implemented for outbound messages.
- With that SEG, you can configure a connection with
- Exceptions are:
- A different email server.
- You must configure a connection with
- Host name: smtp.zivver.com
- Port: 25 or 587
- Security: TLS 1.2 with STARTTLS
- This connection is authenticated by either:
- SMTP credentials.
- SPF implemented for outbound messages.
- You must configure a connection with
- There must be an active Zivver account for the Sender’s email address (From:).
- The Zivver DNS Settings need to be implemented. Then, Zivver can send messages on behalf of the domain(s) that your organization uses to send messages from.
Limitations
Know these limitations when you use a Encryption Gateway.
- Zivver’s Data Loss Protection (DLP) does not apply to messages sent with Zivver Encryption Gateway. You can only use Zivver’s DLP when sending a message using a Zivver client (integration) or Zivver DLP Gateway.
- When a Mail Flow Rule in Microsoft Exchange (or a similar functionality in any other email server or Secure Email Gateway) is not set up correctly or deactivated, the sent message might not be delivered or delivered as a regular email.
- Only when a Recipient receives a notification message and replies within the Zivver Guest Portal, the original Sender will receive this reply securely via Zivver. If the Recipient replies to a message delivered by Zivver via an alternative delivery method, it depends on the recipient’s email server how that reply is secured.
- A reply by the original Sender to a reply received from the Recipient will cause a new Zivver conversation to be created.
Implement Zivver Encryption Gateway
Zivver Encryption Gateway is implemented in your organization’s email server, Secure Email Gateway (SEG), or any other application sending email. To make use of Zivver Encryption Gateway the outbound email is submitted to Zivver’s SMTP Gateway.
Connect to Zivver’s SMTP Gateway.
Connect your email server, Secure Email Gateway (SEG) or sending application to Zivver’s SMTP Gateway by using the following specifications:
- Host name: smtp.zivver.com.
- Port: 587.
- Security: TLS 1.2 with STARTTLS.
- Authentication done by either:
- Providing SMTP credentials that are generated by a Zivver Admin in the Zivver Admin Panel.
- Having SPF implemented for outbound messages. The Zivver SMTP Gateway will check if SPF passes and also verifies that the domain in the From header can submit messages.
Customize which outbound messages are submitted
Your organization can decide on which outbound messages are relayed to Zivver’s SMTP Gateway and which ones are not. For example, you can exclude messages to certain domains. For more information about how to filter those sent messages, refer to third-party documentation. This can be:
- Your email server.
- Your secure email gateway (SEG).
- Your sending application.
Or refer to the chapters below for more information about how to filter out messages in Exchange.
Implement Encryption Gateway in Microsoft Exchange
This chapter describes how to implement Encryption Gateway in Microsoft Exchange.
With the implementation of Encryption Gateway in Microsoft Exchange, you can securely deliver messages when:
- A specific (word in the) subject is used.
- A message and/or an attachment has a certain Sensitivity Label applied (Exchange Online only).
- A specific email address is used as the Sender.
To implement Encryption Gateway in Microsoft Exchange, these changes are necessary:
- Create an Accepted domain (Exchnage On premise only).
- Create a Contact (Exchange On premise only).
- Create a Connector.
- Create a Rule.
Create an Accepterd domain (Exchange On premise only)
Please follow the instruciton in Create an accepted domain in Exchange on premise to create an accepted domain in Exchange On premise.
Create a Contact (Exchange On premise only)
Please follow the instruciton in Create a contact in accepted domain to create a contact in Exchange On premise.
Create a Connector
Encryption Gateway uses a Connector to submit sent messages to the Zivver SMTP Server.
Before you start creating a connector, please send an email to enterprise@zivver.com to request your domain to be added to the Zivver domain allowlist. This is needed to be able to make a connection from Microsoft Exchange Online to the Zivver SMTP Server.
With Microsoft Exchange, an outbound message can be processed only by one Connector. Therefore, know in advance which Connectors are configured in Microsoft Exchange Online. It might not be possible to implement Encryption Gateway, if it is required that a different specific Connector also processes the sent messages. If this is the case or if you need help, send your use case to enterprise@zivver.com.
Please read Create a connector in Exchange Online for the steps to create a Connector in Microsoft Exchange Online.
Please read Create a connector in Exchange On premise for the steps to create a Connector in Microsoft Exchange On premise.
Create a Rule
With a Mail Flow Rule, you can filter sent messages on:
- A specific (word in the) subject is used.
- A message and/or an attachment has a certain Sensitivity Label applied (Exchange Online only).
- A specific email address is used as the Sender.
Once a message has been filtered out, it needs to be submitted to the Zivver SMTP Server, to be able to deliver them securely to the recipient. Unfiltered messages will be delivered unsecurely, as a regular email.
The pages below describe how to:
- Create an Encryption Gateway Rule in Exchange Online for a trigger word.
- Create an Encryption Gateway Rule in Exchnage Online for a Sensitivity Label.
- Create an Encryption Gateway Rule in Exchange Online for a specific sender.
- Create an Encryption Gateway Rule in Exchange On premise for a trigger word.
- Create an Encryption Gateway Rule in Exchange On premise for a specific sender.
Default behavior
Every email submitted to Zivver Encryption Gateway will start a new secure Zivver conversation. Emails with multiple recipients are handled in the following manner:
- ‘To’ recipients and ‘CC’ recipients will become part of the same secure Zivver conversation. There is no distinction between ‘To’ and ‘CC’ recipients.
- For each ‘BCC’ recipient, a separate secure Zivver conversation will be started.
Each recipient will be verified according to the most secure method available to Zivver in the this order of priority:
| Order of priority | Verification method | Used when: | Delivery method |
|---|---|---|---|
| #1 | Zivver Account | This method is automatically applied if the Recipient has their own Zivver account, which is protected with 2FA. | Zivver message notification 1 |
| #2 | NTA 7516 | This method is automatically applied when both the Sender and the Recipient meet the requirements of the NTA 7516. | Direct delivery email |
| #3 | Custom access rights | Access rights are specified in the Zivver access rights header. See below for more detail on how this can be used. | Zivver message notification |
| #4 | Transport security layer | This method is applied if your organization allows transport security compliance as a recipient verification method. | Direct delivery e-mail |
| #5 | Time-based one-time passcode via sms | Either the Sender or someone else within your Zivver organization could have used a shared SMS verification before for this specific Recipient. If the Recipient successfully opened that message, the same SMS verification can automatically be applied to this new message to the same Recipient. | Zivver message notification |
| #6 | Access code verification | Either the Sender or someone else within your Zivver organization could have used a shared Access Code before for this specific Recipient. If the Recipient successfully opened that message, the same Access Code can automatically be applied to this new message to the same Recipient. | Zivver message notification |
| #7 | Email verification | Email verification is used if no other (more secure) verification method is available. | Zivver message notification |
1 Recipients with a Zivver account will receive a Zivver message notification. If they open this notification in an email client with a Zivver client integration installed, they will see the content of the message directly within their email client. If the recipient’s domain belongs to an organization that uses Zivver and that has inbound direct delivery (IDD) enabled, the message will be directly delivered to the recipient’s inbox.
Specifying custom access rights
For every email submitted to the Zivver SMTP Gateway, you can (optionally) specify the verification method and details for the recipient(s). If present, the specified verification method will be used to determine the recipient verification method in line with the order of priority described in the previous section. The verification method for a recipient can be specified using the following custom email header:
zivver-access-right
Zivver supports specification of two different recipient verification methods using this header:
- SMS verification through a time-based one-time passcode.
- Access code verification.
To specify SMS verification, the header should contain the recipient email address, followed by ‘sms’, followed by the phone number of the recipient. To specify access code verification, the header should contain the recipient email address, followed by ‘access-code’, followed by the desired access code. Zivver requires a separate header per recipient. It is possible to specify different access rights per recipient. Below is an example with multiple recipients and different access rights:
zivver-access-right: recipient1@domain.com sms +31612345678
zivver-access-right: recipient2@domain.com sms +31687654321
zivver-access-right: recipient3@domain.com sharedAccessCode 135789
zivver-access-right: recipient4@domain.com sharedAccessCode 246789
Specifying a preference for direct delivery
For every email submitted to Zivver’s SMTP Gateway, it is possible to indicate a preference for direct delivery of the message to the recipient(s) if the receiving mail server meets a specified minimum level of transport security. This provides you with the ability to give preference to direct delivery of specific messages, even if ‘transport security compliance’ is not an enabled verification method for your organization.
If the specified minimum level of transport security is not available, Zivver will fall back to the default behavior described above.
Preference for direct delivery of the message can be indicated using the following custom email header:
zivver-direct-delivery
The minimum level of transport security is split into two email header options:
- ‘tls’ is the minimum version of Transport Layer Security (TLS)
- ‘auth’ is the minimum level of recipient mail server authentication
Zivver currently supports the following values:
| Header option | Supported values | Description |
|---|---|---|
| tls | tls1.2 | This enforces Transport Layer Security version 1.2. |
| auth | certificate-validation | This is a check that the recipient mail server has a valid certificate from a certificate authority (CA), and not a self-signed certificate |
The header option and selected values should be separated by spaces. For example, a complete header would look as follows: zivver-direct-delivery: tls tls1.2 auth certificate-validation
- tls=tls1.2
- auth=certificate-validation
If this header is used, each recipient will now be verified according to the following order of priority:
| Order of priority | Verification method | Delivery method |
|---|---|---|
| #1 | Zivver account | Zivver message notification1 |
| #2 | NTA 7516 | Direct delivery email |
| #3 | Direct Delivery | Direct delivery email |
| #4 | Custom access rights | Zivver message notification |
| #5 | Transport security compliance | Direct delivery email |
| #6 | Time-based one-time passcode via SMS | Time-based one-time passcode via SMS |
| #7 | Access code verification | Zivver message notification |
| #8 | Email verification | Zivver message notification |
See the full table with explanations of each verification method in the ‘default behavior’ section above.
Explicitly fall back to email verification
When direct delivery with the specified minimum level of transport security is not possible, Zivver falls back to the default behavior. See above. There is one exception: By default, Zivver prevents the falling back to email verification if the email verification access code goes through a connection that does not have the minimum level of transport security.
You can override this default. Then, include these custom email header and value:
zivver-minimum-recipient-verification: verification-email
Only when this header is included with the above value, Zivver enables the falling back to email verification. If the header is included but the value is missing or invalid, Zivver prevents the falling back to email verification. If falling back to email verification is not permitted and there is no other verification method available, Zivver returns to the sender of a failed delivery status in a notification.
Attachment handling for direct delivery messages
When an email is directly delivered to the recipient(s), attachments smaller than 10MB in size will be added to the message as a regular attachment. Attachments larger than 10MB in size will be added to the message as secure download links. This is to avoid failed deliveries.
Downloading the attachment via the secure download link will require verification of the recipient. They either need to be logged in to their Zivver account or will be verified using email verification.
Email-verification in this case is always possible: the message has been directly delivered. That means that the required level of transport security was met.