Hi @hnchosla,
Emails going to spam actually depends on a lot of different factors. It is not only on the SMTP that you are using. If the contents of the emails contains a lot of links and appears to be spammy then the email can go to the spam folder. Also, the reputation of the domain from which you are sending the emails can also impact the emails deliverability.
You can test the spammyness of your email using this tool – https://www.mail-tester.com/
To resolve the issue, please check the email contents first and then also check the email and domain reputation from the email sending service that you are using.
Thank you!
