Allow processing of e-mail that have more than 255 characters on subject

Problem definition

Currently when an e-mail has more than 255 characters on the mail field, it will not be processed by JIRA Service Desk mail channel. No error is thrown to the original sender and message is not processed.
On a regular JIRA mail handler, the e-mail will be truncated and processed, although.

Suggestion

Allow processing more than 255 characters or, at least, notify the original sender when the e-mail is not processed.