When receiving mail for a multiple user POP3 account, the ISP should add the e-mail address of the true recipient to a header field at the top of the message. This header field is usually
Received: … For e-mail_ address or
The ISP sometimes adds other information to the e-mail address, such as the domain name.
eg. firstname.lastname@example.org could become email@example.com
If this e-mail address does not exist within WorkgroupMail then the message will be treated as for an unknown recipient.
To overcome this problem, create an additional alias address for each user using the format adopted by the ISP, so that each user has two e-mail addresses
NB. The additional address will only be used by WorkgroupMail for the correct delivery of messages