To Buy SMTP server or SMTP hosting services, you can consider contacting reputable hosting providers or technology vendors that specialize in email infrastructure. Some well-known providers for email-related services include Amazon SES, SendGrid, Mailgun, and more.

When choosing an SMTP server or hosting service, it's important to consider your specific requirements, such as the volume of emails you plan to send, your budget, and any additional features you need (e.g., tracking, deliverability monitoring, API integration).
Source-https://smtpget.com/smtp-service-provider/