User Tools

Site Tools


hints:mail_forwarding

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
hints:mail_forwarding [2021/02/19 06:04]
admin [Backscatter caused by forwarded spam]
hints:mail_forwarding [2021/03/08 09:41] (current)
admin [Mail forwarding causes backscatter]
Line 52: Line 52:
   * [[hints:procmail_classic_linux|Procmail mail filtering in Classic Linux]]   * [[hints:procmail_classic_linux|Procmail mail filtering in Classic Linux]]
   * [[hints:procmail_directadmin|Procmail mail filtering in DirectAdmin]]   * [[hints:procmail_directadmin|Procmail mail filtering in DirectAdmin]]
-  * [[hints:example_procmailrc_file|Hint: example .procmailrc file]]+  * [[hints:example_procmailrc_file|Example generic .procmailrc file]]
  
 ===== Mail forwarding from within your control panel ===== ===== Mail forwarding from within your control panel =====
- 
-**Forwarding mail from within your control panel will forward spam.** 
  
 You can set up mail forwarding from within your [[:Virtualmin]] or [[:DirectAdmin]] control panel. You can set up mail forwarding from within your [[:Virtualmin]] or [[:DirectAdmin]] control panel.
Line 81: Line 79:
 ===== Mail forwarding causes backscatter ===== ===== Mail forwarding causes backscatter =====
  
-Almost all incoming mail includes some amount of spam. Our servers typically reject about 80–85% of all incoming mail because it is diagnosed with high confidence as spam. The 15–20% that is permitted to reach you includes some fraction that is likely spam. Mail forwarding as enabled within the Virtualmin control panel, or as enabled using a '' .forward '' file, will include some small amount of spam.+Almost all incoming mail includes some amount of spam. Our servers typically reject about 80–85% of all incoming mail because it is diagnosed with high confidence as spam. The 15–20% that is permitted to reach you includes some fraction that is likely spam. Mail forwarding as enabled within the Virtualmin or DirectAdmin control panel, or as enabled using a '' .forward '' file, will include some small amount of spam.
  
-If the site that receives this forwarded mail detects spam and rejects it, that will become bounce that our servers will try to return to the original sender. But in most spam, the sender is forged. The bounce will therefore go to some innocent person. This is called [[backscatter]]. Excessive amounts of backscatter may be treated as a type of spam coming from our servers. This may cause our servers to be added to various black lists, causing outgoing mail from our servers to be blocked, and thus causing inconvenience to all users.+If the site that receives this forwarded mail detects spam and rejects it, that will become a delayed bounce that our servers will try to return to the original sender. But in most spam, the sender is forged. The bounce will therefore go to some innocent person. This is called [[backscatter]]. Excessive amounts of backscatter may be treated as a type of spam coming from our servers. This may cause our servers to be added to various black lists, causing outgoing mail from our servers to be blocked, and thus causing inconvenience to all users.
  
 +In the [[:Classic Linux]] environment, if you use the **mailq** command and find any significant amount of queued mail that seems to be to you or from you, quite likely this is backscatter being generated by mail forwarding that you are doing.
 ====== Mail forwarding solutions ====== ====== Mail forwarding solutions ======
  
-There are two solutions.+There are a number of possible solutions.
  
-**Discarding bounced spam automatically**+===== Discarding bounced spam automatically =====
  
 +Our servers try to detect bounced spam and discard it. This works if the rejection message from the receiving site appears to indicate that the site rejected the message because it was diagnosed as spam. This type of bounce is then simply discarded, and does not become backscatter.
  
 +If a receiving site rejects mail as spam but our system doesn't recognize the error message, then it will try to return the bounce to the original sender, and the message will then become backscatter.
  
-Our servers try to detect bounced spam and discard it. This works if the rejection message from the receiving site clearly explains the reason that it rejected the message. This type of bounces is then simply discarded, and does not become backscatter. This is currently implemented in [[:Classic Linux]] only. +===== Having the receiving site pull mail from your mailbox =====
- +
-If a receiving site rejects mail as spam but our system doesn't recognize the error message, then it will try to return the bounce to the original sender, and the message will then become backscatter.+
  
-**Having the receiving site pull mail from your mailbox**+A second solution is to have the receiving site pull mail from your mailbox directly, so you don't have to forward it. Many email sites will fetch your mail from our servers via POP, if you give them your login information. Only **if** you trust such a site with your login name and password, then this mechanism is preferable to normal mail forwarding. Then:
  
-A second solution is to have the receiving site pull mail from your mailbox directly, so you don't have to forward it. Many email sites will fetch your mail from our servers via POP or IMAP, if you give them your login information. Only **if** you trust such a site with your login name and password, then this mechanism is preferable to normal mail forwarding. It does not suffer from the spam problem. Your mail will be safely fetched regardless of a sending domain'spam policies.+  * Your mail will be safely fetched regardless of a sending domain'SPF, DKIM, and DMARC records. 
 +  * Mail fetched in this manner will not become bounced backscatter.
  
-**Combination solutions**+===== Combination solutions =====
  
-One slight disadvantage to having a receiving site pull mail from your mailbox is that there may be a slight delay, of a few minutes, before incoming mail reaches the destination site. A good combination solution is to use **procmail** to forward mail, while not forwarding spam. This makes your mail reach the forwarded destination immediately. Any mail not forwarded because it might be spam is then pulled from the destination site within a few minutes. Almost all mail will be directly forwarded, and any that is not will be pulled via POP.+One slight disadvantage to having a receiving site pull mail from your mailbox is that there may be a slight delay, of a few minutes, before incoming mail reaches the destination site. A good combination solution is to use **procmail** to forward mail, while not forwarding spam. This makes your mail reach the forwarded destination immediately. Any mail not forwarded because it might be spam is then pulled from your mailbox by the destination site within a few minutes. Almost all mail will be directly forwarded, and any that is not will be pulled via POP. Forwarding with procmail is discussed earlier in this document.
hints/mail_forwarding.1613743477.txt.gz · Last modified: 2021/02/19 06:04 by admin