From PostgreSQL wiki
Why won't you remove my post?
There are a number of reasons why we will not remove or modify messages in the archives:
- We want the archives to accurately represent the history of our public mailing lists.
- Messages posted to our mailing lists are archived by other organisations outside of our control both directly, and via our Usenet gateway. Removing a message from our archives would only be the tip of the iceberg.
- Due to the way the archives are stored and occasionally regenerated from archived mailbox files, there is no way to permanently modify a message.
- Removing a message breaks the numbering system used to access subsequent messages which will break any links on websites or other list messages.
- We have limited volunteer resources to run the project (and no non-volunteer resources) and would prefer to use those resources to produce a great DBMS than rewrite history.
E-Mail Disclaimers and Licensing
Some companies or organization add footers to outgoing e-mail messages with that group's e-mail policies, such as this simple example:
- This e-mail is confidential and only for use by the intended recipient.
These disclaimers are incompatible with sending messages to the PostgreSQL mailing lists. When the mailing list is the "intended recipient", that includes all of its current subscribers and the archives. These archives are public, archived, and searchable; they cannot be made confidential.
By choosing to send messages to a PostgreSQL mailing list, you are implicitly granting your permission for that message to be archived in that fashion, regardless of any e-mail disclaimer it might have. And source code submissions to mailing lists such as pgsql-hackers are considered submissions to the PostgreSQL project, falling under the project's PostgreSQL license. Please make sure you have permission to share information with these lists before sending your message.