Send spam reports using the same account it was received on

[dermoth]

Providers seems to recognize their own mail as when I send reports from another account they tend to bounce, and they never did sending back from the same account.

I have multiple account and when I forward to SC the default sending account is used. While it may be hard to figure out which account received an email if they get moved around, a fairly simple and usually correct approach is to just use the outbound server for the account the mails are currently located in.

Since afaik you can't select multiple mails from different accounts (unless there is some merged folder features like outlook I don't know about) multiple sends should be able to easily follow the same rule.

[RobbyZ]

This would be a vital enhancement for people using the registrar contact method

[pscdodd]

This is still true today, the extension seems to use the first account in the list as the "from" address. As a workaround, you can change the account you are sending from by selecting it in the from menu (at least if you are not using the Quick spamcop option.
Note: The mails are still sent, but from the wrong account. This is very confusing, and may result in multiple submissions of the same mail.