If you want to send the same campaign to same target list multiple times go to modules/Campaigns/language/en_us.lang.php
Go to line 347 and delete
āLBL_LOG_ENTRIES_BLOCKEDD_TITLEā => āSuppressed by Email Address or domainā,
Itās supposed to be a safeguard by design so you DONāT send the same email to the same contact twice. If you do, itās possible to trigger their spam filter and your contact wonāt receive future emails.