1. A computer program product comprising a non-transitory computer useable storage medium to store a computer readable program that, when executed on a computer, causes the computer to perform operations comprising: link a web address entry of an address book in an email client to service information from a service registry, wherein the service information corresponds to a web service, wherein the service information from the service registry comprises metadata indicative of invocation procedures for the web service, wherein the service information includes metadata corresponding to a custom user input field for the web service; generate a user input form within an email composer, the user input form comprising the custom user input field corresponding to the service information for the web service; and invoke a service request for the web service via an email message according to user input via the custom user input field of the user input form of the email composer.