Often, companies, universities, organizations, groups, and individuals that manage their mail servers themselves adopt naming conventions that make it straightforward to identify who is the owner of a given email address.
Besides control of the local names, insourcing may provide for data confidentiality, network traffic optimization, and fun.
[4] Not the core product, their email services could lack some interesting features, such as IMAP, Transport Layer Security, or SMTP Authentication —in fact, an ISP can do without the latter, as it can recognize its clients by the IP addresses it assigns them.
It is also possible to run a shim service, providing no access but just forwarding all messages to another account, which does not lend itself to direct use, for example because it is temporary or just less appealing.
[10] The mailbox provider also specifies how users can read their mail, possibly creating SRV records to ease email client configuration, or giving detailed instructions.
This role is based on IETF standards, and, unlike X.400 and other ITU-T works, in and of itself requires no arrangements with local authorities.