Just a post, cause I got a problem with my exported lightmaps from 3ds max
I tried to use this lightmap into unity and it looks like this. (same problems for all my lightmaps on all objects into unity)
I thinking that the problem comes from 3ds max
But I tried to load this lightmap as a diffuse texture into 3dsmax and it works perfectly without these white lines from my UVs.
Thanks a lot !