Mailgun 的定价页面在此 - Flexible Email Delivery & API Pricing Plans - Transactional Email API Service For Developers | Mailgun
对于 brevo，您可以参考其文档 - https://help.brevo.com/hc/en-us/articles/7924908994450-Send-transactional-emails-using-Brevo-SMTP
在设置自托管实例时，您需要了解一些 SMTP 知识。