The VSVL (Variable Strange Visiting Limit) is one kind of send end technic to spam control. It's not a simple send end control techninc, is a system which needs the participation from the mail transmission and receival. For clearly explained this system, only discusses the VSVL mail servers and communications within each other as the examples here. Other cases refer to REALISM please.
IF the VSVL system work, must establish a VSVL host and website first, and some mail servers which perform the VSVL rules as the client, all of these clients are called VSVL mail servers.
The VSVL servers use a special contacts grouping, named FriendList and HelloList. If received an email, the address will enter the FriendList; if send an email not in FriendList we called StrangeVisiting in here, and the address will enter the HelloList.
- The rule of send quota: The StrangeVisiting email is limitd by StrangeVisitingQuota, each this email was send, the StrangeVisitingQuota minus 1, the address enter the FriendList and the HelloResendQuota minus 1 at the same time; or the address is in the HelloList, the HelloResendQuota minus 1, and the StrangeVisitingQuota minus 1 if the HelloResendQuota equal the initial value before the email send. If the address is in the FriendList, the FriendResendQuota minus 1 only. Can not send any email if the correspond Quota is zero, and all Quotas are initialized everyday.
- The quota initialization: All the quota initialization can be designed as any positive integer for need. Maybe the HelloResendQuota and the FriendResendQuota initialize as 3 is a good choose, and the StrangeVisitingQuota initialization as 1 is the relentlessest choose.
- The rule of quota adjustment: When a mail was received, if the source mailbox is FriendList then FriendResendQuota were initialized as FriendResendQuotaMax, else if in the HelloList and the HelloResendQuota less than initialization the HelloResendQuotaMax then enter the FriendList and the StrangeVisitingQuota plus 1, other case enter the FriendList simply. The Strange visit quota is adjusted by credit mechanism: The StrangeVisitingCounter plus 1 when the StrangeVisitingQuota minus 1. The StrangeVisitingMax plus 1 when it equals the StrangeVisitingCounter and the counter become zero. The StrangeVisitingMax minus InformCounter when received a spam inform and InformCounter plus 1. One day example, if the InformCounter beginning is M, the received spam inform is N, the StrangeVisitingMax are minus by N*((N-1)/2+M). The InformCounter minus one everyday auto, and the StrangeVisitingCounter not increase if the InformCounter is bigger than zero.
- The rule of group, CC, BCC and forward: Any address were managed by other rules separately.
- The function of the VSVL host and website: Issuance and maintenance the VSVL mail server list (IP list), which can be think as a mail server white list. Manage the spam inform and VSVL technic server.
- Mail receive: VSVL mail server hold the VSVL mail server list local, and refurbish from the VSVL host everyday. When a VSVL server ask a SMTP it contain the VSVL statement, and the receive VSVL mail server can ensure if the ask is form the VSVL mail server by compare the connect IP with the VSVL mail server list. It receive all mails form VSVL mail server and refuse others (remember only discusses the VSVL mail servers and communications within each other as the examples here).
- Feedback mechanism: One can inform a spam mail if sure. And the spam inform is send to VSVL host and source VSVL mail server separately by one key.
The introduction in the Chinese is more clearly show our idea, please refer to here ......
敬请参阅中文介绍，如译文有误，欢迎指正