I'm getting the same weird errors with zMail. I turned it off and reinstalled Postal to see if perhaps it was just the mail mods screwing up and it still errors. Not sure what the deal is.
Though I get two errors when I open my mail I just can't figure out how to fix them.
One if a framexml error and the other is with sellfish onevent and/or onmouseover or soemthing.
I'm sure it'll sort itself out. They work just fine but I had to turn off bugsacks sound on error. It was driving me nuts "Fataility, Fataility, Fataility, Fataility, Fataility, Fataility, Fataility, Fataility!"