Summary
Purchasing a block of Class C IP addresses for hosting mail servers is a multifaceted process that requires careful consideration of various technical, reputational, and procedural aspects. Before acquisition, thorough vetting of IP brokers and investigation of IP health using blocklists and WHOIS records is crucial to avoid inheriting a history of spam abuse. ARIN requires justification for IPv4 requests based on planned use, emphasizing the need for a clear strategy. Proactive monitoring of IP reputation, implementing authentication mechanisms like SPF, DKIM, and DMARC, and adhering to SMTP standards (RFC 5321) are essential for maintaining deliverability. A proper IP warmup schedule, setting up a reverse DNS (rDNS), and considering the geographical location of the IP block also contribute to a successful email sending infrastructure. While historical reputation issues are often resolvable, rehabilitating damaged IPs can be time-consuming, and ongoing attention to neighboring IP reputation is necessary.
Key findings
- IP Health & Reputation: Checking IP reputation via blocklists and monitoring services is paramount.
- Broker Due Diligence: Thoroughly vet IP brokers to ensure legitimacy and avoid inheriting compromised IPs.
- ARIN Requirements: Meet ARIN's IPv4 request justification requirements based on planned use.
- Authentication Protocols: Implement SPF, DKIM, and DMARC for enhanced email authentication and deliverability.
- Standards Compliance: Adhere to SMTP standards (RFC 5321) for interoperability and to avoid spam filters.
- IP Warmup Essential: A gradual IP warmup is crucial for establishing a positive sending reputation.
- PTR record: Setup a PTR record matching the hostname.
Key considerations
- Pre-Purchase Investigation: Investigate IP health, reputation, and broker legitimacy before committing to a purchase.
- Justification Documentation: Prepare thorough documentation for ARIN justifying IPv4 request based on planned use and network infrastructure.
- Continuous Monitoring: Continuously monitor IP reputation, bounce rates, and spam complaints.
- Network Configuration: Set up reverse DNS (rDNS) records and ensure proper network configuration.
- Warming Strategy: Develop and execute a gradual IP warmup strategy.
- Proactive Management: Be prepared to actively manage IP reputation, address blacklistings, and maintain compliance with SMTP standards.
- Neighbor Impact: Understand that neighbors within Class C block can impact your reputation.
What email marketers say
11 marketer opinions
Purchasing a block of Class C IP addresses for hosting mail servers requires careful consideration of several factors to ensure optimal email deliverability and sender reputation. Key aspects include checking IP reputation against blacklists and services like SenderScore, Spamhaus, and Talos. Monitoring the reputation of neighboring IPs within the same Class C block, implementing proper authentication mechanisms such as SPF, DKIM, and DMARC, and establishing a reverse DNS (rDNS) record. A proper IP warmup strategy, selecting a reputable IP broker, and considering the geographical location of the IP block are also crucial for success.
Key opinions
- IP Reputation: Checking IP reputation is important, you can use services like SenderScore, Spamhaus, and Talos.
- Neighbor Reputation: Be aware of the reputation of neighboring IPs within the same Class C block.
- Authentication: Implement SPF, DKIM, and DMARC records to improve deliverability and protect against spoofing.
- Reverse DNS: Set up a reverse DNS (rDNS) record to verify the legitimacy of your sending server.
- IP Warmup: A gradual IP warmup strategy is essential for establishing a positive sending reputation.
- PTR record: Ensure PTR record matches mail server.
Key considerations
- IP Reputation Monitoring: Proactively monitor IP reputation metrics like sender score, bounce rates, and spam complaints.
- Authentication Setup: Properly configure SPF, DKIM, and DMARC records to authenticate your emails and prevent spoofing.
- IP Warmup Schedule: Plan a gradual IP warmup schedule to avoid triggering spam filters and establish a good sending reputation.
- Broker Vetting: Thoroughly research and vet IP brokers to ensure you are purchasing clean IPs with no prior spam history.
- Geographical Relevance: Consider the geographical location of the IP block and its relevance to your target audience.
- PTR Record: Setup your PTR record correctly to point to your mail server.
Marketer view
Email marketer from SocketLabs.com emphasizes that while dedicated IPs offer more control, you should still be aware of the reputation of neighboring IPs within the same Class C block. If other users on the same block engage in spammy behavior, it can negatively impact your sending reputation.
17 Sep 2022 - SocketLabs.com
Marketer view
Email marketer from EasyDMARC explains that setting up a Domain-based Message Authentication, Reporting & Conformance (DMARC) record helps protect your domain from email spoofing and phishing attacks. DMARC builds upon SPF and DKIM to provide a more robust authentication mechanism.
18 Oct 2021 - EasyDMARC.com
What the experts say
5 expert opinions
When purchasing a block of Class C IP addresses for hosting mail servers, several key considerations emerge from expert advice. Historical reputation issues are generally resolvable, but rehabilitating a damaged IP range can be time-consuming. While acquiring IPs from ARIN is typically straightforward and IPs are recoverable, carefully vetting brokers is crucial to avoid addresses with a history of spam. Checking IP health through blocklist lookups and WHOIS record examination is essential to ensure legitimacy and mitigate deliverability risks. Announcing routes and notifying bogon list maintainers is also advised.
Key opinions
- Reputation Recovery: IP ranges can usually be recovered even with prior reputation issues.
- ARIN Acquisition: Acquiring IP addresses from ARIN is typically a simple process.
- Broker Vetting Critical: Carefully vet brokers to avoid purchasing IPs with a history of spam.
- IP Health Check: Check IP health via blocklists and WHOIS records before purchase.
Key considerations
- Rehabilitation Effort: Be prepared to invest time in rehabilitating IPs if they have been previously used for spam.
- Broker Due Diligence: Thoroughly vet IP brokers to ensure the cleanliness and legitimacy of the IP addresses they are selling.
- Initial IP Assessment: Conduct thorough checks of IP health using blocklists and WHOIS records to identify potential risks.
- Network Configuration: Remember to announce routes and notify bogon list maintainers after acquiring the IP addresses.
- Wrangling: Be prepared for a steep learning curve, managing your own IP block comes with challenges.
Expert view
Expert from Email Geeks explains that historical reputation issues are rare and resolvable. He also seconds the point that wrangling it all after purchasing the IPs will be a challenge.
7 Apr 2023 - Email Geeks
Expert view
Expert from Email Geeks shares experience advising clients on buying IPs, stating it's generally easy to get them from ARIN. She reinforces that IP ranges can always be recovered, neighbors across /24 boundaries are unlikely to cause harm, and ARIN cannot reclaim IPs once registered. She advises to announce routes and notify the bogons list.
1 Sep 2023 - Email Geeks
What the documentation says
4 technical articles
When purchasing a block of Class C IP addresses for hosting mail servers, it's crucial to adhere to documented standards and guidelines. ARIN requires justification for IPv4 address requests based on current and planned use. Understanding and avoiding IP address blacklists, as detailed by Spamhaus, is essential for email deliverability. Ensuring the use of public IP addresses, as opposed to private ones defined in RFC1918, is a must. Finally, adhering to SMTP standards outlined in RFC 5321 is vital for email interoperability and to avoid spam filters.
Key findings
- ARIN Justification: ARIN requires justification for IPv4 requests based on utilization and planned use.
- Blacklist Avoidance: Understanding and avoiding IP blacklists is crucial for deliverability.
- Public IP Addresses: You must use public IP addresses, not private ones defined in RFC1918.
- SMTP Standards: Adhering to SMTP standards (RFC 5321) is vital for interoperability and avoiding spam filters.
Key considerations
- Usage Planning: Accurately document and plan your IP address usage to meet ARIN's justification requirements.
- Blacklist Monitoring: Implement continuous monitoring for IP address blacklisting to promptly address any issues.
- IP Address Type: Verify that you are requesting and using public IP addresses, not private ones intended for internal networks.
- SMTP Compliance: Ensure your mail servers and sending practices fully comply with SMTP standards outlined in RFC 5321.
Technical article
Documentation from Spamhaus.org details the importance of understanding and avoiding IP address blacklists. Being listed on a blacklist can severely impact email deliverability. Regular monitoring and adherence to best practices can help prevent blacklisting.
23 Apr 2022 - Spamhaus.org
Technical article
Documentation from RFC-Editor.org details that you ensure you are requesting Public IP addresses from ARIN. RFC1918 specifies the block of IP address which are private. You cannot send directly from private IP addresses.
4 May 2024 - RFC-Editor.org
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