[Chapter 9] 9.5 Things to Try
Author: Bryan Costales & Eric Allman
Date: 1999-01-06T18:36:08Z

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| Chapter 9 Rule Set 0 |

## 9.5 Things to Try

- Devise an error-handling rule that will detect an address that contains a username and an `@` character but no host part.

- Is it possible to have text in the LHS that is literally `$+`, rather than an operator with the same characters?

- The client.cf file uses `$#error` to handle errors in rule set 0. Examine your site's sendmail.cf file to see if it is legal to use `$#error` in other rule sets.

9.4 The error Delivery Agent |  | 10. Rule Set 3