You can also set
-mintxfee to lower than 0.00001; and you should set
-minrelaytxfee to the same value for your own node to accept it.
Add these to your bitcoin.conf file (0.1sat/b minimum):
# [relay]
minrelaytxfee=0.000001
# [wallet]
mintxfee=0.000001
Warning:
- By doing so, your node will start to relay <1sat/b TXs.
- The <1sat/b TXs that you will create still wont be relayed by nodes with default minrelayfee.