The message below will be output in EMS log if the network is disconnected before the schedule snapmirror transfer is over.
[xxxx: sm_logger_main: smc.snapmir.schd.trans.overrun:error]: Scheduled transfer from source volume 'xxxx:xxxx' to destination volume 'xxxx' is taking longer than the schedule window. Relationship UUID 'xxxx'.
A email notification can be considerred to setup by filter event "smc.snapmir.schd.trans.overrun".
For details to setup filter event, please refer to How to configure event filter and event notification for email destination