由 Onno Ekker （開發者） 發表於 Feb. 1, 2018 · 永久網址

Hi, the error message you get is a server error. You have to check with your mail provider for the exact error. There can be many reasons for this error, but probably you've sent too many messages in a short period of time and you have to wait a bit to be able to send messages again. You can try to prevent this from happening, by setting the number of concurrent SMTP-connections to a lower value, for instance to 1 in Mail Redirect's Options.