The personal message feature is not available to newer members in order to reduce the opportunities for spammers and scammers.
If you have saved personal messages you wish to keep for posterity, you should copy them to your personal computer. In future when spam PMs are discovered, the administration, at its sole discretion, may choose to dump all personal messages for all members across the entire forum, without notice.
Simple Machines and Lewis Media, the developers of the software we use for our forum, as well as the staff of SDC feel strongly about the importance of privacy in personal communications. The software we use is not set up to allow administrators or moderators to view the personal messages of others and will not be hacked to do so. That makes removing objectionable PMs an all or nothing proposition. In order to delete one objectionable message, I must delete ALL PMs. If you receive an objectionable personal message, click on "Report to admin" in the lower right corner of the message. That will send a copy of the message to the administrator. Administration cannot recover or view a PM once it has been deleted unless it is first sent to them in a report.
Folks caught abusing the PM feature by using it to bypass forum rules will lose the privilege or simply be banned at the discretion of the administration.