We faced a similar issue a month ago, even while using the Pro plan of SendGrid, which provides a dedicated IP for email delivery. Despite this, Gmail still blocked some of our emails due to reputation issues. To address this, we are currently focusing on improving our delivery practices, such as adhering to email authentication protocols (e.g., SPF, DKIM, DMARC), cleaning our email list, and sending to engaged users only.

I recommend prioritizing increasing your delivery rate and sender reputation, as this will help resolve many deliverability issues. However, it's worth noting that we are still blocked by Gmail in some cases, which emphasizes how important it is to maintain consistent sending habits and build a good reputation over time.

If you have enabled click tracking in SendGrid, consider setting up a custom domain for URL redirection to maintain your brand identity and avoid potential reputation issues. If click tracking isn’t enabled, you can skip this step.

If your email volume is below 100 emails per day, there’s no urgent need to switch to a paid plan or another service provider unless the free plan limitations are affecting your business. Switching to a paid plan or another provider might make sense if you need higher sending limits, a dedicated IP, or better support. However, improving your sender reputation is a critical step that applies regardless of the email service you use.