Limitations of outbound relay through Mailprotector


Mailprotector provides the option to relay outgoing email to enable secure, human-to-human communication that is protected by SafeSend, and provides solutions against reputation damage, data loss, and encryption by policy.

The focus of Mailprotector's relay (or smarthost) is secure, human email communication. The relay is not designed or managed for marketing, bulk/mass, or transactional email communication.

Defining Email Communication Differences

Bulk or Mass Email

An email that is sent to a large group of recipients is considered bulk or mass email in most cases. This is especially true when an email involves more than twenty recipients, is generated by an application or mail merge process, and does not present a "directed conversation." Bulk or mass emails may have individualized salutations, but the message is broad.

Bulk and mass email is not supported by Mailprotector as an accepted email relay. Attempts to relay bulk or mass emails through Mailprotector may result in held messages, disabled relay services on the offending sender address up to and including a permanent ban.

Marketing Email

Email campaigns intended to advertise, market, inform, or sell to a broad audience are considered marketing or promotional emails. Newsletters are also considered marketing emails for Mailprotector's acceptable use of the outbound relay.

Marketing email is a form of bulk or mass email, which can increase the likelihood of messages to be held and relay disablement actions taken on the offending sender address.

Transactional Email

Transactional emails are typically messages generated by a device or application. Common transactional emails are phone system voicemail or fax notifications, multi-function device scan-to-email attachments, and web-based forms that create an email.

Messages from a device or application may work with Mailprotector's relay, but the support of transactional emails is best-effort only. The outbound relay makes no exceptions on security filtering and provides no whitelisting options to allow outbound messages to skip the security layers. Therefore, transactional emails that are held for review or cause the disablement of relay for a sender address should be expected. The best practice is to use an alternate email relay for transactional messaging.

Best Practice Recommendations

Bulk and Marketing Communication

Managing the reputation of IP addresses and infrastructure for mass email activity is a very different process than a regular, human business communication. This is a primary reason that Mailprotector's outbound relay considers this a violation of acceptable use.

Newsletters are best managed and have the highest rate of deliverability when sent from a service provider designed for this type of email communication. Providers other Mailprotector partners have mentioned success with include:

Transactional Communication

Transactional emails are a "gray-area" because messages sent from a multi-function device or phone system to users inside of a company are often considered acceptable; by Mailprotector and the CloudFilter and SafeSend security layers. However, there is no guarantee that the functionality will be maintained. If a change in behavior from the device or application creates a hold or disablement, only best-effort support will be provided.

Transactional emails are best served by email providers designed for transaction-based activity. Much like bulk email, the IP reputation management and deliverability strategies are different than a secure, business communication.

The best practice for emails coming from phone/fax systems, CRM/ERP systems, multi-function devices, and web-based forms is an email relay with transactional volume support. These can be SMTP authentication-based or API-based services.

The most common providers other partners have had success with are:

Acceptable Use Violations

Mailprotector may consider other behaviors through the outbound relay as violations of acceptable use. The definition may change as the email security landscape, and best practice behaviors adjust over time.

Other outbound relay violations that can cause a sender address to be disabled include, but are not limited to:

  • Excessive emails to non-existent addresses; high email bounce rate that exceeds 2% of delivery attempts
  • Questionable or malicious content
    • Creating 'RE:' or 'FW:' subject lines on original emails
    • Excessive marketing language in email signatures
    • Link or URL obfuscation
  • Suspicion or evidence of compromised mailbox account
  • Reports of abuse from third-party email providers

If you have questions or concerns, please contact the Partner Success team for assistance.

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