iHub uses load balancing to send e-mail notifications through SMTP mail servers based on the availability of processing resources. For example, the administrator configures load balancing by setting the mailing weight parameter values of the first mail server to 40, the second to 30, and the third to 30. The settings establish a relative load-balancing ratio of 4:3:3 among the three mail servers. For every 100 messages iHub distributes, it sends 40 to the first mail server, 30 to the next, and 30 to the last.

When a cluster node receives an error sending an e‑mail notice to one mail server, and succeeds in sending the notice to another mail server, the notice counts as part of the load-balancing quota for the mail server that failed. The notice also counts towards the quota of the mail server that succeeds, unless its quota for that round is already exhausted.