How can I send co-branded emails for clients without harming my reputation?
Michael Ko
Co-founder & CEO, Suped
Published 5 Jul 2025
Updated 22 Aug 2025
8 min read
Sending co-branded emails for clients can be a powerful way to expand reach and leverage established trust, but it comes with significant risks to your hard-earned sender reputation. The core challenge lies in navigating recipient expectations and consent, especially when the sender is not the primary brand they initially engaged with. This scenario requires a delicate balance of technical configuration, strategic list management, and transparent communication to ensure your emails land in the inbox and not the spam folder.
My client, a service provider, has opted-in subscribers who purchased through their services. While these subscribers consented to receive communications from my client, they primarily recognize the end brand, not the service provider. The concern is that if we send co-branded emails from my client’s domain, the unfamiliarity could lead to high complaint rates, ultimately damaging our sender reputation.
Maintaining a strong sender reputation is crucial for deliverability. A poor reputation can lead to emails being blocked or routed to the spam folder, impacting engagement and ROI. This is particularly true when introducing a new sender identity, even if it’s a co-brand. Let's explore the best practices to manage this carefully.
The challenge of implicit consent
The fundamental principle of email deliverability is consent. Even if your client (the service provider) technically collected the email address and obtained an opt-in, the crucial question is, "Who did the customer ask to receive email from?" Recipients generally consent to receive emails from the brand they directly interacted with or purchased from. If your client is a 'middle-man' or a service provider working on behalf of another brand, the end customer's perceived consent might only extend to the primary brand, not your client.
This discrepancy can create a 'grey area' of consent. A paper trail of opt-ins is vital for legal compliance but doesn't guarantee a positive recipient experience. If recipients don't recognize the sender in a co-branded email, they are far more likely to mark it as spam. These spam complaints are a direct signal to Internet Service Providers (ISPs) that your emails are unwanted, swiftly damaging your IP and domain reputation. You can learn more about building a strong sender reputation on Allegrow's email sender and domain reputation guide.
To mitigate this, it is essential to review the original welcome messaging and opt-in process. Was it explicitly clear to the subscriber that they would receive emails from both the primary brand and the service provider (your client)? If not, directly sending from your client's domain without further action is risky. Even in a B2B context, where relationships can be more nuanced, recipient recognition is paramount.
Understanding consent for co-branded emails
The crucial distinction is who the recipient expected to hear from when they opted in. If they only know the end brand, your client’s direct emails might be perceived as unsolicited, regardless of legal opt-in status. This leads to higher spam complaints and potential blocklistings (or blacklistings).
Strategic list management and engagement
Before sending any co-branded campaigns, especially to a list that hasn't been recently mailed, strict list hygiene is non-negotiable. Passing the entire segment through a validator is a smart first step, focusing only on sending to valid addresses. This significantly reduces bounce rates and avoids hitting spam traps, which can instantly tank your sender reputation. A high bounce rate, particularly hard bounces, signals to ISPs that your list is outdated or poorly managed, triggering deliverability issues.
For lists with ambiguous consent or low recognition of your client, a strategic re-opt-in process is highly recommended. Instead of directly sending marketing emails from your client, the primary brand (the one the customer recognized during purchase) should send an opt-in invitation. This email introduces your client (the service provider) and asks recipients to explicitly opt in to receive further communications from them. This weeds out unresponsive or negatively responsive subscribers, ensuring a cleaner, more engaged list for future co-branded sends. This proactive approach helps improve email deliverability by focusing on genuine interest.
If a full re-opt-in isn't feasible, consider a slow, gradual warming approach. Segment the list and send small batches, closely monitoring key metrics like open rates, click-through rates, and crucially, spam complaint rates. If complaint rates spike, immediately pause and re-evaluate your strategy. You can learn more about how to send to an unengaged email list without harming your reputation.
Direct send approach (high risk)
Consent assumption: Assumes recipients are aware of and consented to direct emails from your client, the service provider.
Recipient recognition: Low likelihood of immediate recognition if the primary brand was the main point of contact.
Reputation impact: High risk of increased spam complaints and unsubscribes, severely damaging sender reputation (both IP and domain reputation).
List health: May expose hidden spam traps or inactive addresses, leading to further deliverability problems.
Re-opt-in campaign (recommended)
Explicit consent: Primary brand sends an invitation for recipients to explicitly opt into communications from your client.
Recipient engagement: Ensures that only genuinely interested subscribers receive future emails, leading to higher engagement.
Reputation protection: Significantly reduces spam complaints and bounce rates, safeguarding your client's (and your own) email reputation.
Brand alignment: Clearly establishes the partnership and sets expectations for future communications from your client.
Technical foundations and authentication
Proper email authentication is the backbone of good deliverability, especially when sending co-branded emails. Ensure that SPF, DKIM, and DMARC records are correctly configured for the sending domain. For co-branded messages, pay close attention to the `From` header and `Return-Path` to ensure they align with your authentication records. This alignment (known as DMARC alignment) tells receiving mail servers that the email is legitimately from the stated sender, building trust and improving inbox placement. You can learn more about DMARC, SPF, and DKIM.
When sending co-branded emails, it's generally best to use a subdomain of your client’s primary domain, such as marketing.yourclientdomain.com. This allows you to establish a separate sender reputation for co-branded initiatives without directly jeopardizing the reputation of the root domain. If issues arise, they are contained to the subdomain, protecting the main brand's email channels. However, even with a subdomain, proper authentication for both domains is critical.
Implement a robust DMARC policy from day one. Start with a p=none policy to gather insights from DMARC reports, identifying any authentication failures without affecting deliverability. Gradually, you can move to a p=quarantine or p=reject policy as confidence grows. DMARC provides crucial visibility into how mail servers are processing your authenticated emails, which is invaluable for co-branded sends. Regular monitoring of DMARC monitoring and blocklist monitoring is essential.
The content of your co-branded email needs to be crystal clear about the relationship between your client and the other brand. Use both brands' logos prominently and consistently throughout the email. The `From` name should also reflect both entities, for example, "[Primary Brand] & [Your Client]". This helps recipients immediately understand who is sending the email and why they are receiving it. Be careful about changing the From Name too frequently.
Beyond branding, the email copy must explicitly state the nature of the partnership and why the recipient is receiving this particular email. Remind them of their prior interaction or purchase that led to this communication. Setting clear expectations about the value proposition, frequency, and type of content they will receive is crucial for long-term engagement and minimizing complaints.
Finally, ensure your emails comply with all relevant anti-spam laws, such as CAN-SPAM in the U.S. or GDPR in Europe, even for B2B communications. This includes providing a clear and easy-to-use unsubscribe link. A transparent and compliant approach reinforces trust and professionalism, which are key components of a healthy sender reputation. You can review factors affecting email deliverability for more insights.
Element
Direct Send (Risky)
Co-branded with Re-opt-in (Recommended)
From name
Single brand, potentially unrecognizable to recipients.
"Primary Brand via Your Client" or similar.
Branding
Only your client's logo, confusing recipients.
Both logos prominently displayed, clear visual alignment.
Introduction
No explicit explanation of the relationship, leading to confusion.
Clear explanation of the partnership, reminding recipients of their consent.
Expectations
Unclear what to expect next from the sender.
Sets clear expectations on content, frequency, and value.
Views from the trenches
Best practices
Always prioritize recipient consent and recognition above all else when co-branding emails for clients.
Use dedicated subdomains for co-branded sends to isolate reputation risks and maintain primary domain integrity.
Implement SPF, DKIM, and DMARC for all sending domains and subdomains, ensuring proper alignment.
Conduct thorough list hygiene, validating all email addresses before any initial send.
Clearly communicate the partnership and your client's role in the email content, subject lines, and 'From' names.
Common pitfalls
Assuming implied consent: Believing a past purchase automatically grants permission for a new sender.
Ignoring recipient recognition: Sending from an unfamiliar brand, leading to high spam complaint rates.
Neglecting email authentication: Sending emails without proper SPF, DKIM, and DMARC configurations.
Sending to an unsegmented or uncleaned list: This can quickly damage sender reputation.
Lack of transparency in co-branded messaging: Not clearly explaining who is sending and why.
Expert tips
Consider a double opt-in process for any new co-branded list to confirm genuine interest and reduce spam complaints.
Monitor email engagement metrics closely, especially unsubscribe and complaint rates, to detect issues early.
If the primary brand has a strong relationship, have them introduce your client with a soft opt-in campaign.
Review sender identity guidelines, for instance, Google and Yahoo’s, to ensure compliance.
Segment your list based on engagement and gradually introduce co-branded emails to highly engaged segments first.
Expert view
Expert from Email Geeks says that deliverability is entirely dependent on how recipients perceive the mail. If they think it's spam, reputation is destroyed, regardless of your client's internal paper trail of consent.
2024-08-12 - Email Geeks
Expert view
Expert from Email Geeks clarified that the client likely logged somebody else's consent, not their own. The crucial factor is who the customer (recipient) actually asked to receive emails from during the initial opt-in.
2024-08-12 - Email Geeks
Navigating co-branded email for reputation protection
Sending co-branded emails for clients without harming your reputation is a challenging but achievable goal. It hinges on a proactive and meticulous approach to consent, technical configuration, and transparent communication. Prioritize recipient recognition and experience above all else. Legal consent is important, but true deliverability success comes from earned permission and positive engagement.
By carefully validating lists, implementing robust authentication, considering strategic re-opt-in campaigns, and ensuring clear co-branding in your content, you can leverage the power of partnerships while safeguarding your valuable sender reputation. This will ultimately lead to higher inbox placement and a stronger return on investment for your email marketing efforts.
