A method comprising: within a single communication application running on a computer, wherein the single communication application is configured to send a message using a plurality of different types of electronic communications services: receiving, at a computer, a first user input including a first partial identifier for a first intended recipient of a message to be sent by a sender; determining, by the computer, based at least in part on the first partial identifier, a first set of candidate account addresses each associated with one of a plurality of electronic communication services; presenting to the sender, by the computer, the first set of candidate account addresses; receiving, by the computer, a user selection of one of the first set of candidate account addresses as a first selected candidate account address of the first intended recipient for the message, wherein the first selected candidate account address is associated with a first one of the plurality of electronic communication services; determining, by the computer, in response to the user selection, a sender account address associated with the sender to be used for sending the message to the first intended recipient at the first selected candidate account address; receiving a second user input including a second partial identifier for a second intended recipient of the message; determining, by the computer, based at least in part on the second partial identifier, a second set of candidate account addresses each associated with one of the plurality of electronic communication services; determining a subset of the second set of candidate account addresses that are associated with the first electronic communication service; presenting to the sender, by the computer, only the subset of candidate account addresses; receiving, by the computer, a user selection of one of the subset of candidate account addresses as a second selected candidate account address for the second intended recipient for the message; and sending the message to the first selected candidate account address and the second selected candidate account address from the sender account address. within a single communication application running on a computer, wherein the single communication application is configured to send a message using a plurality of different types of electronic communications services: receiving, at a computer, a first user input including a first partial identifier for a first intended recipient of a message to be sent by a sender; determining, by the computer, based at least in part on the first partial identifier, a first set of candidate account addresses each associated with one of a plurality of electronic communication services; presenting to the sender, by the computer, the first set of candidate account addresses; receiving, by the computer, a user selection of one of the first set of candidate account addresses as a first selected candidate account address of the first intended recipient for the message, wherein the first selected candidate account address is associated with a first one of the plurality of electronic communication services; determining, by the computer, in response to the user selection, a sender account address associated with the sender to be used for sending the message to the first intended recipient at the first selected candidate account address; receiving a second user input including a second partial identifier for a second intended recipient of the message; determining, by the computer, based at least in part on the second partial identifier, a second set of candidate account addresses each associated with one of the plurality of electronic communication services; determining a subset of the second set of candidate account addresses that are associated with the first electronic communication service; presenting to the sender, by the computer, only the subset of candidate account addresses; receiving, by the computer, a user selection of one of the subset of candidate account addresses as a second selected candidate account address for the second intended recipient for the message; and sending the message to the first selected candidate account address and the second selected candidate account address from the sender account address.