In addition to any fee for extra POP mailboxes, e-mail data transfer (bandwidth) is counted toward your account's monthly data transfer allowance, just like Web site data transfer usage. However, in most cases, e-mail usage is a very small amount.
As an example: if you receive 100 average-sized text e-mail messages per day, that's less than 20 MB data transfer usage per month. Since even our basic account includes hundreds of times that amount, it's unlikely to lead to extra charges.
However, if you regularly receive dozens of multi-megabyte file attachments by e-mail, the usage would be higher, and could cause extra charges if your total usage exceeds the amount normally included in your plan. We'd notify you in advance if that were likely to happen in any month.
To review your data transfer usage, see Account Usage.