Ingress-nginx currently does not support TCP or UDP services. The Helm chart will expose SMTP service as a LoadBalancer (it creates a new AWS ELB). You can get the LoadBalancer/ELB information by running the following command:
kubectl get services `kubectl get services --namespace=alfresco | grep email | awk '{print $1}'` --namespace=alfresco
This produces an output similar to the one below - the ELB DNS name is shown in the EXTERNAL-IP column.
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE alert-fly-alfresco-cs-email LoadBalancer 100.XX.33.188 a1dXXXXXab11eaac6702XXXf87b-XXXXXXXXXX.eu-west-1.elb.amazonaws.com 1125:30554/TCP 2d