Mail protocol support.
| Class | DomainDeliveryBase | A base class for message delivery using the domains of a mail service. |
| Class | SMTPDomainDelivery | A domain delivery base class for use in an SMTP server. |
| Class | ESMTPDomainDelivery | A domain delivery base class for use in an ESMTP server. |
| Class | SMTPFactory | An SMTP server protocol factory. |
| Class | ESMTPFactory | An ESMTP server protocol factory. |
| Class | VirtualPOP3 | A virtual hosting POP3 server. |
| Class | POP3Factory | A POP3 server protocol factory. |