A message topic works like a JMS topic in that it it publishes messages to subscribers either synchronously (via receive()) or asynchronously (via onMessage() callback).

A topic provides read-only access to messages as there can be multiple subscribers and synchronising edits would be challenging.

A topic can be configured using a filter to define a subset of messages to publish.

The current RegEx matches to most cases very well but the expression for validate if the E-Mail pattern is correct implement not the full RFC.
^[_A-Za-z0-9-\+]+(\.[_A-Za-z0-9-]+)@" + "[A-Za-z0-9-]+(\.[A-Za-z0-9]+)(\.[A-Za-z]{2,})$

Add functionality that user can be able to add attachements to the email