[Feature] smtp without auth

[bombaata]

Description / 功能描述

Hello, can you allow basic SMTP notifications without mandatory authentication on port 25 please ?

Motivation / 请求动机

For simple setups

Miscellaneous / 其他

No response

Contribution / 贡献代码

• I am interested in contributing a PR for this! / 我乐意为此提交代码并发起 PR！