I can repeatable put uvm in a situation where it runs out of memory
trying to copy an amap. I think there are PRs about similar probems.

Is this being worked on by anyone, and is there anything I can do to
help fix this?

What causes this is emacs trying to send a rather large attachment in
multiple parts, spawning multiple MTAs at once. I assume that the
object that is about to be copied is somehow mmaped by emacs. The
malloc that fails is the second one in amap_alloc1 (in amap_copy). If
I got the ddb output right it tries to copy a map with 9489 pages
(~37MB), this on a 128M machine.

/Johan