"High probability of spam" when sending transactional emails

Hi all

I’m using the API to try to send transactional emails to users. However, despite setting up my domain and getting it authenticated by Brevo, all the emails are being rejected as spam. I’ve tried sending to Outlook, gmail, and 3rd party mail servers (cpanel type ones) but they all get rejected with some form of spam message.

Given that Brevo is happy with my DKIM and DMARC settings, is there anything I can do to ensure emails are at least delivered to the mailbox, if not the actual inbox?

The emails don’t have anything spammy in them, they are just « Welcome to the app » type emails for an app for distillers.

Olly

Hi Olly,

Thanks for reaching out, and sorry to hear your transactional emails are being blocked — that’s frustrating, especially when your DKIM and DMARC are already verified.

Authentication is a great first step, but spam filters look at a few more signals beyond that. Here are some things worth checking:

Sender reputation and IP warm-up If your account is new, the shared IP you’re sending from may not yet have an established reputation. Sending even a small volume of emails consistently over time helps build trust with mailbox providers. Sudden activity from a fresh account can trigger spam filters regardless of content.

Your sending domain’s reputation Even with DKIM/DMARC in place, if your domain is brand new, it won’t have any reputation history. Mailbox providers (especially Gmail and Outlook) are cautious with emails from new domains. This improves naturally over time as you send legitimate mail and recipients engage with it.

Email content Even simple « Welcome » emails can be flagged if the HTML is not clean, or if they contain certain patterns. A few things to double-check:

  • Make sure you’re sending from a professional address on your own domain (not a free provider like Gmail or Yahoo)
  • Avoid URL shorteners in links
  • Keep your HTML clean and valid

For a full overview of what affects deliverability and how to improve it, our best practices guide covers all the key areas: https://help.brevo.com/hc/en-us/articles/360020418259-Best-practices-for-email-deliverability

Let us know if you have more details about your setup and we can dig in further!