Something like this, maybe? (I didn’t test)
curl -X POST -H "Content-Type: application/json" \
-d "{
"active": "1",
"domain": "domain.tld",
"local_part": "info",
"name": "Full name",
"password": "atedismonsin",
"password2": "atedismonsin",
"quota": "3072",
"force_pw_update": "1",
"tls_enforce_in": "1",
"tls_enforce_out": "1",
"tags": [
"tag1",
"tag2"
]
}" https://mailcow.domain.tld/api/v1/add/mailbox