You can find SMTP Service using this tool.
SMTP stands for Simple Mail Transfer Protocol and its primary purpose is to handle the sending, receiving, and relaying of email. Common inbox providers like Gmail have default smtp servers but you can change them to custom ones like Mailgun's. This will route your emails through Mailgun's servers which can be advantageous if you want to send a lot of emails and make sure it actually gets delivered into the inbox.
An attacker might use the disclosed information to harvest specific security vulnerabilities for the application identified.
Only use components that do not have known vulnerabilities, only use components that when combined to not introduce a security vulnerability, and ensure that a misconfiguration does not cause any vulnerabilities.