SQL Log Shipping Cross Domain

Hi,

I have 2 separate domains between which I don't have the option of setting up a trust. One is a production environment, the other a DR environment.

In order to get the SQL 2012 log shipping process to work, I need to be able to pass-through authentication for identical domain accounts on each domain, i.e.

DOMAIN1\sql.user

DOMAIN2\sql.user

Both have the same password, yet I can't seem to get pass-through to work. Is there some trick I'm missing here? I've been playing about with various GPOs but so far nothing has worked.

I'd rather not have to resort to local accounts.

Thanks

Russ