FINRA Rule 3110.06

If the procedures in place do not require that all incoming and outgoing written correspondence to be reviewed before use or distribution, they must provide for:

1. Education and training on procedures governing correspondence.
2. Documentation of education and training.
3. Surveillance and follow-up to ensure that the procedures are implemented and followed.

In practice, item No. 3 would likely require the capture of such incoming and outgoing correspondence in order to ensure continuing compliance.