Summary
Sending internal system notifications using the same ESP as transactional emails presents deliverability challenges. While not inherently catastrophic, the impact hinges on several factors. Mailbox providers assessing mail streams differently, proper email authentication (SPF, DKIM, DMARC), and maintaining impeccable list hygiene are critical. Internal notifications generating high spam rates, bounce rates, or SMTP errors can negatively impact sender reputation and domain/IP reputation, affecting transactional email deliverability. Segregating mail streams using dedicated IPs and different DKIMs, warming up IPs, and continuously monitoring IP/domain reputation are vital. Optimizing SMTP configurations is also beneficial.
Key findings
- Mail Stream Recognition: Whether Google and other ISPs recognize internal and external streams as different affects deliverability; using DKIM can help.
- Sender Reputation: Sending internal system notifications affects sender reputation, impacting transactional email deliverability.
- IP Reputation: Low engagement with certain mail streams or poor sending practices from one mail stream can negatively affect IP and domain reputation of other streams.
- List Hygiene: Poor list hygiene leads to high bounce rates and spam complaints, harming sender reputation.
- Authentication: Improper authentication leads to emails being flagged as spam, impacting sender reputation.
- SMTP errors: SMTP errors from invalid recipients can negatively impact sender reputation
Key considerations
- Dedicated IPs: Using dedicated IP addresses to separate mail streams is a viable strategy for isolating reputation and deliverability issues.
- Segmentation: Segment internal and external email sending to boost deliverability.
- Email Authentication: Ensuring proper email authentication (SPF, DKIM, DMARC) for all email streams is essential for establishing trust.
- List Management: Maintaining impeccable email lists by removing unengaged or bounced emails is crucial for high deliverability.
- IP Warm-up: When launching new IPs, warming them up gradually is crucial to establishing a positive sending reputation.
- Reputation Monitoring: Regularly monitoring IP and domain reputation through tools like Google Postmaster Tools and Microsoft SNDS is essential for identifying and addressing potential issues.
- SMTP Configuration: Ensure you have the correct SMTP configuration to ensure emails send smoothly
What email marketers say
9 marketer opinions
Sending internal system notifications using the same ESP as transactional emails can negatively impact deliverability. Factors such as shared IP reputation, list hygiene, authentication, engagement, and sender reputation are all affected. High bounce rates, spam complaints, and unauthenticated emails from internal notifications can damage the sender's reputation and subsequently harm the deliverability of transactional emails. Proper email authentication (SPF, DKIM, DMARC), maintaining clean email lists, segmenting mail streams, using dedicated IPs, warming up IPs, and monitoring IP reputation are key to mitigating these risks. Correctly configuring SMTP connections can also improve deliverability.
Key opinions
- IP Reputation: Sending different types of emails from the same IP can negatively impact IP reputation, especially if marketing emails have low engagement or internal emails generate spam complaints.
- List Hygiene: Poor list hygiene for internal notifications, such as sending to old or invalid addresses, can lead to high bounce rates, signaling poor sending practices.
- Authentication: Improperly authenticated internal notifications can be flagged as spam, negatively impacting the overall sending reputation.
- Sender Reputation: Sending internal system notifications affects sender reputation, which is key to good deliverability.
- Engagement: Low engagement with certain mail streams can negatively affect sender reputation of other streams.
Key considerations
- Dedicated IPs: Consider using dedicated IP addresses to separate mail streams and isolate issues.
- Segmentation: Segment internal and external email sending to increase deliverability.
- Authentication: Ensure proper email authentication (SPF, DKIM, DMARC) for all email streams.
- List Management: Maintain clean email lists by removing unengaged or bounced emails.
- Warm-up IPs: When using new IPs, ensure they are warmed up slowly.
- Monitor Reputation: Consistently monitor IP and domain reputation through tools like Google Postmaster Tools and Microsoft SNDS.
- SMTP Configuration: Configure the system to have an adequate number of SMTP connections to prevent delays and avoid impacting deliverability negatively.
Marketer view
Email marketer from Reddit explains that poor list hygiene for internal notifications (sending to old or invalid addresses) can lead to high bounce rates. High bounce rates signal poor sending practices and can hurt your overall deliverability.
3 Aug 2023 - Reddit
Marketer view
Email marketer from Litmus Blog explains that proper email authentication (SPF, DKIM, DMARC) is crucial for establishing trust with mailbox providers. If internal notifications are not properly authenticated, they can be flagged as spam and impact your overall sending reputation.
29 Jun 2024 - Litmus Blog
What the experts say
4 expert opinions
Sending internal system notifications alongside transactional emails using the same ESP can impact deliverability, though it's not inherently catastrophic. The key is whether mailbox providers recognize the streams as distinct. Poorly managed internal lists and unwanted notifications can generate spam reports, harming sender reputation. Segregation of mail streams is advisable, especially if deliverability issues arise. Warming up a new IP address is essential for establishing a positive reputation when introducing new internal email systems.
Key opinions
- Mail Stream Recognition: Deliverability impact hinges on whether mailbox providers recognize internal and transactional streams as distinct. DKIM can help differentiate.
- List Management Impact: Poorly managed internal lists can cause increased spam reports and degrade sender reputation, affecting transactional email deliverability.
- IP Warm-up: New IP addresses require a warm-up period to establish a positive reputation when sending internal emails.
Key considerations
- Segregation: Consider segregating internal and transactional mail streams, particularly if internal notifications are frequently unwanted or if deliverability issues are observed.
- List Hygiene: Implement rigorous list management practices for internal notifications to minimize spam complaints.
- IP Warm-up: Follow a gradual IP warm-up process to establish a positive sending reputation before sending high volumes of internal notifications.
- DKIM Differentiation: Use different DKIM settings for transactional and internal streams to signpost the different types of emails.
Expert view
Expert from Spamresource explains that a poorly managed list is a huge cause of spam reports. If a business' internal email list is poorly maintained, and emails are sent to addresses that are not expecting them, this can generate high spam complaints which will affect the sender's reputation and impacting transactional emails.
17 May 2022 - Spamresource
Expert view
Expert from Email Geeks explains that whether the different mail streams affect deliverability depends on if Google recognizes them as different. Different DKIM d= would be one way to explicitly announce they’re different. Also to fix badly handled internal campaigns.
18 Jun 2021 - Email Geeks
What the documentation says
4 technical articles
Sending internal system notifications can affect transactional email deliverability through several mechanisms. SMTP errors from invalid recipients can harm sender reputation. High spam rates from irrelevant content or outdated lists in internal notifications negatively impact domain reputation with major providers like Gmail. Monitoring IP reputation via Microsoft SNDS is crucial, as issues with internal notifications can impact reputation with Outlook and Hotmail. Maintaining low bounce rates by promptly removing hard bounces and repeatedly soft-bouncing addresses from both internal and external lists is also critical for preserving sender reputation.
Key findings
- SMTP Errors: SMTP errors from internal notifications (e.g., invalid recipients) can negatively impact sender reputation.
- Domain Reputation: High spam rates from internal notifications damage domain reputation, especially with Gmail.
- IP Reputation: Issues with internal notifications affect IP reputation with Microsoft's Outlook and Hotmail.
- Bounce Rates: High bounce rates, if not promptly addressed, decrease sender reputation.
Key considerations
- Error Monitoring: Actively monitor SMTP error codes to identify and resolve issues with internal notifications.
- Reputation Monitoring: Regularly monitor domain reputation via Google Postmaster Tools.
- IP Reputation Monitoring: Monitor IP reputation through Microsoft SNDS to understand how Microsoft views your sending practices.
- List Hygiene: Promptly remove hard bounces and repeatedly soft-bouncing addresses from both internal and external lists to maintain low bounce rates.
- Content Relevance: Ensure internal notifications contain relevant content and are sent to valid, engaged recipients to minimize spam complaints.
Technical article
Documentation from SparkPost explains that to maintain low bounce rates to keep a good sender reputation it is important to remove addresses that hard bounce immediately. Also it is important to remove emails that have soft bounced multiple times. This is important for internal and external lists.
3 May 2025 - SparkPost
Technical article
Documentation from Microsoft SNDS shares that monitoring your IP reputation is essential for understanding how Microsoft views your sending practices. Issues with internal notifications can impact your IP's reputation with Outlook and Hotmail.
8 Aug 2022 - Microsoft
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