While it may not be the most egregious design break, the way it seems to happen at random, and the fixes we have to employ, make it an almost rage-inducing bug. Despite Microsoft being fully aware of the bug, we’ve seen no fixes on Outlook’s end.
So, why do these white lines appear in your Outlook emails? Although we don’t know the exact reason for this odd behavior, the leading theory is that it has to do with heights that are odd numbers.
If these white lines are causing you a headache there are some potential quick fixes to help you get rid of them, at least temporarily:
Change up your font sizes and heights.
For some folks, the fix is as simple as changing font sizes from odd numbers to even numbers. For example, if you have a font size of 13px or 15px, try converting it to 14px.
You can also try manually changing heights, font sizes and line-heights to achieve the same outcome.
Add a ghost break.
Often adding a ghost break will temporarily fix the rogue white lines in Outlook. Similar to ghost columns, a ghost break is a line break that we add targeted only towards Outlook.
