Thank you much.
Using ctrl+u did not have any effect in my Opera Mail.
In the mean time Jeremy from Firetrust Support for Mailwasher emailed me this:
Hi Lode,
Yes, MW can indeed show the headers and full email as below....
Click the "Show email info" link just above the preview pane, (Click View>>Preview Pane if you do not have this enabled) then click the "Source tab.
That will show the raw text of the email, to copy it, click in the email and click ctrl A to select all, then click Ctrl C to copy.
...................
But when I log in on this page https://www.spamcop.net/ and tap on Report spam no place appears where I can paste something. This appears though:
Welcome, Lodewijk. You have 14.6M bytes available.Your average reporting time is: 2 hours; Great!
Bounce error
Your email address, xxxATxxxDOTxxx has returned a bounce:
Subject: Delivery Status Notification (Failure)
Reason: 5.1.0 - Unknown address error 550-'Sorry, we do not accept connections from=
Please ensure your email account is reliable, then click below (and then this appears in a box to tap on:
[Problem resolved.]
But that problem is not resolved. On this other page which appears after have I logged in and then logged out from the above mentioned page this one appears: https://www.spamcop.net/mcgi?action=loginform
There says: For reporting-only account holders:
Log into https://members.spamcop.net
I don't remember seeing that before, and I can't log in there with my username and password. But would that be the page one can copy-paste headers? Or is that normally done on the first mentioned page where I always logged in to confirm it is spam that I had Mailwasher send to Spamcop?