SMS Subdomain sharing with email

[Silvio6]

Could using the same subdomain for both SMS and email impact my email sending reputation?
For example, if my SMS channel generates a lot of spam complaints or opt-outs, could that negatively affect the reputation of the email subdomain in any way?

[SatheeskannaK · Accepted solution]

@Silvio6 

• It is a best practice, and often a technical necessity, to utilize distinct subdomains for different communication channels, specifically email and SMS.
• You can't use the same subdomain for both channels.
• A simple and effective strategy is to introduce a channel-specific prefix to the email subdomain. For example: As I mentioned in this thread, if your email subdomain is something like mktg.brand.com, and you have delegated it, you might pick a prefix appropriate for SMS URLs (e.g., sms.mktg.brand.com) to setup SMS subdomain.
• The fundamental reason for this separation lies in the management and protection of sender's reputation. Email Service Providers (ESPs) and mobile carriers maintain separate reputation scores for the domains/infrastructure used to send messages.
• Independent Reputational Impact: An important point to understand is that the deliverability and reputation issues associated with one channel do not typically cross over and contaminate the other.
• SMS Spam/Opt-Outs: High levels of spam complaints or opt-out requests generated through your SMS channel (due to unwanted text messages or poor list hygiene) will primarily impact your short code or messaging service's reputation with mobile carriers. These actions will not negatively affect the sender's reputation or the deliverability of your dedicated email subdomain.
• Email Spam/Blacklisting: Similarly, if your email domain faces blacklisting or a decline in inbox placement due to high spam rates, this reputational damage is isolated to the email infrastructure and will not compromise your SMS messaging performance or compliance.
• This isolation is a key protective measure, ensuring that a performance or compliance issue in one channel does not necessitate a complete domain migration across all communication platforms. By maintaining separate, clearly designated subdomains (and infrastructure), you can manage and troubleshoot each channel's deliverability and reputation independently.

[Silvio6]

Thanks for the clarification. Final question: when you say "It is a best practice, and often a technical necessity, to utilize distinct subdomains for different communication channels, specifically email and SMS.", by utilize distinct subdomains you mean this? mktg.brand.com | sms.mktg.brand.com or a completly different subdomain for SMS that's not linked with "mktg.brand.com"? For example mktg.brand.com | sms.myBrandA.com

[SatheeskannaK]

@Silvio6 I recommend using mktg.brand.com and sms.mktg.brand.com because they maintain the root domain. In contrast, sms.mybrandA.com is an entirely separate domain from sms.brand.com. This decision should be made in consultation with your organization's policies and requires coordination with the IT (DNS) team.

[Silvio6]

Thanks so much for your help.