It looks to me like the rows are just compressed. Probably something to do with how the editor in webmail interprets the table HTML that's pasted from LibreOffice. Something similar happens when pasting from OnlyOffice, where some columns are compressed while others are not. 

You can check the code view by expanding the toolbar in the editor (if it's not already) and clicking the < > icon, then adjusting the column width manually. You should also be able to adjust the column width manually, in editor view, by selecting the right column bar and moving it. As an aside, I've yet to run into an online HTML editor that does a great job of handling copy/paste from any Office-type app into an email. Google's isn't terrible, but even it compresses column widths. 

"Copy" the above, that works indeed, the <> code part is WAY too advanced for my users. And dragging works, but some people can't figure it out.

I figured the Open Office integration of late caused something... 

anyways, thank you