System for instant messaging the sender and recipients of an e-mail message

A system comprising:

• at least one processor;
• and
• at least one non-transitory computer-readable storage medium storing instructions that, when executed by the at least one processor, cause the system to:
• receive, over a network, a first communication from a sender via a first communication system;
• identify, from the first communication, users party to the first communication;
• determine, in response to receiving the first communication, whether the identified users party to the first communication are online on a second communication system by:
• extracting addresses of the identified users;
• removing domain information from the addresses to obtain user identifiers;
• performing a reverse look-up process using the user identifiers;
• and
• present, based on determining that one or more identified users of the identified user party to the first communication are online on the second communication system, an option within the first communication system to initiate a second communication with the one or more identified users via the second communication system, wherein the option to initiate the second communication is provided only when the one or more identified users are online on the second communication system.

A non-transitory computer-readable medium storing instructions that, when executed by at least one processor, cause a client device to:

• receive, over a network, a first communication from a sender via a first communication system;
• identify, from the first communication, users party to the first communication;
• determine, in response to receiving the first communication, whether identified users party to the first communication are online on a second communication system by:
• extracting addresses of the identified users;
• removing domain information from the addresses to obtain user identifiers;
• performing a reverse look-up process using the user identifiers;
• and
• present, based on determining that one or more identified users of the identified users party to the first communication are online on the second communication system, an option within the first communication system to initiate a second communication with the one or more identified users via the second communication system, wherein the option to initiate the second communication is provided only when the one or more identified users are online on the second communication system.