In our application we are implementing the Send As feature from Gmail client. https://support.google.com/mail/answer/22370
We are setting the From, To and Reply To headers accordingly to the settings that are set for the external account. Are there other headers that should be set when sending message in behave of external account? For example when we have set another SMTP server for the current external account.
Well, according to User Messages API Document, these are all the headers you need to add:
Users.messages: send
Sends the specified message to the recipients in the To, Cc, and Bcc headers. Try it now or see an example.
This method supports an /upload URI and accepts uploaded media with the following characteristics:
Maximum file size: 35MB Accepted Media MIME types: message/rfc822
Be sure to be authorized first, and apply best practices on sending to external accounts.
