If you have a browser which supports tabs, here's an easy way of dealing with the "failed sending email" error when you make a post.
Hopefully it will help reduce the number of duplicated posts. The record so far has been 6 copies of one post... (no names!)
Right-click on the "post reply" button and select "Open in new tab".
Make your post as usual in that new tab and when it's completed (error or not) after "submit", go back to the original tab.
On the original tab, showing the thread before your post, have your browser do a page refresh.
There's your post...
You can now close the other tab from which you made the post.
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Giraffe: a ruminant with a view.