What are some free or affordable alternatives to SendGrid now that their free tier is gone?

I'm currently developing a small e-commerce application and used to rely on SendGrid's free tier for sending transactional emails like order confirmations and contact forms. With the free plan no longer available, I'm on the lookout for alternatives that offer a solid free plan or a low-cost option. My expected email volume is under 100 emails per day, and I'm hoping to find a service with easy integration since I use Spring Boot for my backend. Any recommendations would be greatly appreciated!