Methods, devices, signals, and systems are provided in a message routing architecture which provides improved capabilities for integrating “digital” communication through email messages with “analog” communication through voice and/or fax or pager messages. Email can be addressed using nothing more than a standard telephone or fax number. If the registered owner of the telephone or fax number has a corresponding email address, then the invention converts the telephone or fax number to the email address for delivery and uses standard email delivery systems to deliver the message. If no conventional delivery email address is known, or if the message sender or recipient specify multiple delivery modes, then the email message content is transformed into voice, pager and/or fax content and delivered to the recipient using the telephone or fax number which was specified as the email address. Familiar telecommunications services such as call forwarding and selective call blocking can also be used with messages that originate as email. The invention also supports use of telecommunications numbers as indexes into databases which contain public key certificates, to make it unnecessary for a proposed message recipient to provide its public key expressly in advance to each particular proposed message originator.