The long/detailed story is here:

Summary is that Outlook 2016 for Windows often add "weird" lines at the bottom of some table cell and those lines are coloured like the body bgcolor, so you mainly see them if your main content background color is different from your body bgcolor.

This doesn't happen in Outlook 2007/10/13 and other clients. Of course this doesn't happen on Outlook 2016 for Mac, because it doesn't use Word for rendering.

I started thinking it was related to the use of "cellspacing", but proved it is not only cellspacing. I thought it was my template, but I've been able to reproduce it with the Mailchimp drag/drop editor.

Three darker horizontal lines not in the template, but rendered by Outlook 2016

Anyone else fighting with this issue? It seems it is very frequent, but I didn't find anyone complaining about this around....