Problem trying to send mail via Orbcomm satellite link

using the provided Q52Omni plug-in sample, I’m trying to use the command
to send an email via the satellite network, as documented in the aplication note.
But, after some time transmitting, I always receive:
rsp->status=10 (tx attempt failed, re-queued)

What might be the problem here? I’ve tried dozens of times…

Thanks for your help.

ps: there doesn’t seem to be a board for satellite specific questions…