使用Mautic发邮件进垃圾，Firebase是否支持rDNS记录？

Let's cut to the chase: Firebase Hosting does NOT support configuring custom reverse DNS (rDNS) records. Here's why, plus what you can actually do to fix your spam folder issue:

Why Firebase Can't Handle rDNS #

Firebase Hosting uses shared IP addresses for all its hosted sites. Reverse DNS is tied exclusively to a single, dedicated IP address—since you don't own or have exclusive control over the IPs assigned to your Firebase site, you can't set a custom rDNS record for them.

A Critical Clarification for Your Email Problem #

Wait a second—let's make sure we're not mixing things up here. Reverse DNS for email deliverability applies to the IP address of your email sending server, not your website's hosting IP (Firebase's IPs). Your tech team is right that rDNS is key for avoiding spam folders, but it's not related to your Firebase-hosted website itself—it's about the server that's actually sending your Mautic emails.

Actionable Fixes to Get Your Emails Out of Spam #

Here are tailored steps to resolve this:

• If Mautic runs on a separate server: Reach out to your server provider (like DigitalOcean, AWS EC2, etc.)—most let you configure rDNS for your server's public IP through their control panel. Pair this with setting up SPF, DKIM, and DMARC records for your domain, and you'll see a big improvement in deliverability.
• If you're hosting Mautic on Firebase (uncommon): Firebase Hosting doesn't natively support PHP (required for Mautic), so you're probably using Cloud Run or App Engine. You can assign a static external IP to these services, then set up rDNS for that IP via Google Cloud's VPC Network console.
• The easiest, most reliable fix: Use a dedicated email service provider (ESP) like SendGrid, Mailgun, or Postmark with Mautic. These services handle all deliverability heavy-lifting—rDNS, SPF, DKIM, DMARC, and IP reputation management—out of the box. Just configure Mautic to send emails through their API or SMTP relay, and your spam rates will drop dramatically.

Even if you could magically set rDNS for Firebase's IPs, it wouldn't help your emails—shared hosting IPs have mixed reputations, and mail providers would still flag emails coming from them as high-risk unless you're using a dedicated email sending setup.

内容的提问来源于stack exchange，提问作者Anthony Tran