Well, both postal codes are valid according to this link;
http://www.canadapost.ca/cpotools/apps/fpc/personal/findAnAddress?execution=e3s1
You find it by using the "Find a Postal Code" link, then using reverse search, which turns into "Find an address"
The 0X0 address is the Post office in Reston, and the 0L0 address is Melita. They are NOT close together.
Time to email the customer and ask them to straighten it out, I think.
Imagination will often carry us to worlds that never were. But without it we go nowhere. Carl Sagan