How do email 'from' addresses and subdomain alignment affect email deliverability and Spam Assassin scores?
Michael Ko
Co-founder & CEO, Suped
Published 20 Jun 2025
Updated 19 Aug 2025
7 min read
When sending emails, the 'From' address is one of the first things recipients see, and it plays a significant role in how mailbox providers and anti-spam filters perceive your messages. It’s not just about what appears to the end-user, but also how it technically aligns with your sending infrastructure. Misalignment here can lead to significant deliverability issues, pushing your emails into the spam folder, or even getting your domain blocklisted (or blacklisted).
A common challenge I often see is confusion around the various 'From' addresses and domains involved in email sending, particularly when subdomains are in play. Understanding how these elements interact, and how they contribute to your sender reputation, is crucial for ensuring your emails consistently reach the inbox. This includes knowing how systems like SpamAssassin evaluate these factors.
The 'From' address you specify in an email is more complex than it might appear. It comprises two main parts: the 'Display Name' (e.g., "Suped Support") and the 'Email Address' (e.g., "support@suped.com"). This is what the recipient sees and is formally known as the RFC5322.From header. Alongside this, there are behind-the-scenes domains that authentication protocols like SPF and DKIM use to verify your sending legitimacy. These include the RFC5321.MailFrom address (often called the Return-Path or Envelope From), and the domain used in your DKIM signature.
Alignment, particularly DMARC alignment, refers to the practice of ensuring that the domain in the visible 'From' address matches, or is a subdomain of, the domains used in your SPF and DKIM authentication. When these domains align, it signals to mailbox providers that the email is legitimate and not a spoofing attempt. Conversely, a lack of alignment can raise red flags, making your emails appear suspicious.
For SPF, alignment means the domain in the RFC5321.MailFrom (Return-Path) address matches the RFC5322.From domain. For DKIM, it means the domain specified in the 'd=' tag of your DKIM signature aligns with the RFC5322.From domain. Achieving strong alignment across these authentication methods is a cornerstone of modern email deliverability. I find that proper configuration of DMARC, SPF, and DKIM is foundational to building trust with mailbox providers and avoiding spam filters.
A common issue arises when the 'From' address uses a different domain or subdomain that is not properly authenticated. For instance, if your visible 'From' address is hello@gotosea.com but your emails are sent from a subdomain like offers.gotosea.com without correct DMARC policy in place, this could lead to deliverability problems. Ensuring consistent domain alignment across all sending parameters is key to improving email deliverability and boosting brand recognition.
The strategic use of subdomains
Many email senders, especially those managing high-volume campaigns, opt to use subdomains for various types of email traffic. For example, you might use marketing.yourdomain.com for promotional emails and transactional.yourdomain.com for order confirmations and password resets. The primary advantage of this strategy is reputation isolation. If your marketing emails encounter deliverability issues and end up on a blocklist, your transactional emails sent from a different subdomain are less likely to be affected.
However, using subdomains doesn't automatically guarantee protection for your main domain. If the subdomains are not properly authenticated with SPF, DKIM, and DMARC, or if the 'From' address on these subdomains is misaligned, it can still negatively impact your overall domain reputation. It's essential to configure authentication records for each subdomain to ensure proper alignment and prevent deliverability issues. This is especially true when considering the impact of domain reputation on subdomains.
Main domain strategy
Benefits:
Simplicity: Easier to manage DNS records for a single domain.
Brand consistency: All emails visibly originate from your core brand.
Drawbacks:
Higher risk: Any deliverability issue can impact all your email streams.
For senders with diverse email programs, like marketing, transactional, and internal communications, I generally recommend using subdomains. This approach allows you to build and maintain separate sender reputations for each email type, minimizing the risk of one stream negatively affecting another. However, it requires careful setup of DNS records, including SPF, DKIM, and DMARC, for each subdomain. For example, for best practices regarding subdomain usage, consider a dedicated strategy for each.
A common mistake is using a generic or free email domain (like gmail.com) as your 'From' address for commercial or bulk sending, even if your underlying technical domains are aligned. This can bypass DMARC enforcement and appear suspicious to filters, leading to lower deliverability. Always use a domain you control and have properly authenticated.
SpamAssassin and alignment scores
SpamAssassin is an open-source anti-spam platform that assigns a score to incoming emails, helping mail servers determine if a message is spam. While its direct influence on major global mailbox providers has decreased over the years in favor of proprietary systems, it is still used by many smaller mail servers, hosting providers, and even some large mailbox providers in certain regions (like Orange.fr and SFR in France). Therefore, understanding its scoring mechanisms can still be valuable.
SpamAssassin has specific rules that flag 'From' address and subdomain misalignments. For instance, if your RFC5322.From address (e.g., hello@gotosea.com) is on a different domain than your RFC5321.MailFrom (Return-Path) address (e.g., bounce@offers.gotosea.com), SpamAssassin might assign a penalty. This lack of alignment can be seen as a characteristic of phishing or spoofing attempts. The same applies if your DKIM 'd=' domain doesn't align.
SpamAssassin Rule
Description
Impact on Score
FROM_DOMAIN_FAKE
The 'From' domain appears to be spoofed or doesn't match other technical domains.
Adds points
FROM_FM_DOM_GENERIC
The 'From' address uses a generic free email domain (e.g., hotmail.com) for non-personal use.
Adds points
DMARC_POLICY_NONE
The sending domain has a DMARC policy set to 'p=none' which is less restrictive.
Can add points
A high SpamAssassin score can significantly impact your email deliverability, especially for recipients whose mail servers use it. While a high score doesn't necessarily mean an email will be blocked outright, it increases the likelihood of it being filtered to the spam folder or even rejected. To improve your score, you need to identify the rules your email is triggering, often by analyzing the email headers.
To mitigate SpamAssassin penalties related to 'From' address and subdomain alignment, ensure all your sending domains and subdomains are properly authenticated with SPF, DKIM, and DMARC. Crucially, verify that your RFC5322.From domain aligns with your SPF and DKIM authentication domains. This consistent alignment builds trust and signals legitimacy, helping to reduce your spam score and improve your overall email deliverability.
Views from the trenches
Best practices
Always ensure DMARC is configured with strict alignment for both SPF and DKIM.
Use subdomains to separate different email streams, such as marketing and transactional.
Ensure SPF, DKIM, and DMARC are correctly set up for every sending subdomain.
Regularly monitor your email authentication reports to detect any misalignment issues.
Common pitfalls
Assuming SpamAssassin is irrelevant without checking your audience's mailbox providers.
Using a 'From' address from a different domain or subdomain without proper DMARC alignment.
Not having private domains set up for all your sending domains within your ESP.
Ignoring the Return-Path domain and only focusing on the visible 'From' address.
Expert tips
Prioritize DMARC alignment above all, as it's critical for modern deliverability.
Even if SpamAssassin isn't universally used, some European providers still rely on it.
For large-volume senders, isolating reputation through subdomains is a smart long-term strategy.
Remember that engagement metrics like open and click rates also heavily influence inbox placement.
Expert view
Expert from Email Geeks says that alignment is crucial for email deliverability in 2025.
2025-05-30 - Email Geeks
Expert view
Expert from Email Geeks explains that if you want to change your 'From' address to a different domain, that domain must be properly set up to sign with DKIM for strict alignment.
2025-05-30 - Email Geeks
Optimizing for inbox placement
The relationship between your email's 'From' address, subdomain alignment, and deliverability is undeniable. While the landscape of spam filtering is constantly evolving, with many major providers moving beyond traditional SpamAssassin scores, the fundamental principles of sender identity and authentication remain paramount. Consistent and proper alignment across your visible 'From' address and your underlying authentication domains is crucial for building and maintaining sender trust.
By strategically using subdomains and meticulously ensuring alignment for SPF, DKIM, and DMARC, you can significantly improve your chances of reaching the inbox. This proactive approach not only helps you pass through stringent spam filters, including those that still use SpamAssassin, but also safeguards your sender reputation against potential issues, ensuring your email program's long-term success.
gmail.com) as your 'From' address for commercial or bulk sending, even if your underlying technical domains are aligned. This can bypass DMARC enforcement and appear suspicious to filters, leading to lower deliverability. Always use a domain you control and have properly authenticated.
Orange.fr and 
SFR in France). Therefore, understanding its scoring mechanisms can still be valuable.
hotmail.com) for non-personal use.
