Rejecting false "mail from" addresses: Difference between revisions
No edit summary |
No edit summary |
||
Line 2: | Line 2: | ||
By default any connection made to ZCS postfix and declares "mail from: local sender" (even if it is not) - the connection/email is accepted for local delivery. This wiki provides steps to block such connections. Once following is configured, postfix will accept "mail from: local sender" only if the connection made from a hosts in "mynetworks" OR the sender is sasl authenticated. | By default any connection made to ZCS postfix and declares "mail from: local sender" (even if it is not) - the connection/email is accepted for local delivery. This wiki provides steps to block such connections. Once following is configured, postfix will accept "mail from: local sender" only if the connection made from a hosts in "mynetworks" OR the sender is sasl authenticated. | ||
1. Modify "smtpd_sender_restrictions". We are adding a check before allowing a normal smtp connection. Allowing hosts in mynetwork, then allowing sasl authenticated too. Then a check for local domain address. If its true - the connection will be rejected. '''[This steps is for ZCS 7.x and older version only]'''. | |||
su - zimbra | su - zimbra | ||
zmlocalconfig -e postfix_smtpd_sender_restrictions="reject_unknown_sender_domain, permit_mynetworks, permit_sasl_authenticated, check_sender_access hash:/opt/zimbra/postfix/conf/access_table, permit" | zmlocalconfig -e postfix_smtpd_sender_restrictions="reject_unknown_sender_domain, permit_mynetworks, permit_sasl_authenticated, check_sender_access hash:/opt/zimbra/postfix/conf/access_table, permit" | ||
For '''ZCS 8.x''', open the file /opt/zimbra/conf/zmconfigd/smtpd_sender_restrictions.cf and add this line in the bottom and save the file. | |||
%%contains VAR:zimbraServiceEnabled antivirus^ check_sender_access hash:/opt/zimbra/postfix/conf/access_table%% | |||
'''Remaining steps are same for all versions.''' | |||
2. Create the file "/opt/zimbra/postfix/conf/access_table" and add your domain(s) to it. | |||
localdomain.com REJECT | localdomain.com REJECT | ||
anotherlocaldomain.com REJECT | anotherlocaldomain.com REJECT | ||
Line 15: | Line 21: | ||
anotherlocaldomain.com REJECT You're not me! | anotherlocaldomain.com REJECT You're not me! | ||
3. Create the hash of "/opt/zimbra/postfix/conf/access_table". | |||
postmap /opt/zimbra/postfix/conf/access_table | postmap /opt/zimbra/postfix/conf/access_table | ||
4. Restart zmmtactl. | |||
zmmtactl restart | zmmtactl restart | ||
Revision as of 14:27, 5 November 2013
By default any connection made to ZCS postfix and declares "mail from: local sender" (even if it is not) - the connection/email is accepted for local delivery. This wiki provides steps to block such connections. Once following is configured, postfix will accept "mail from: local sender" only if the connection made from a hosts in "mynetworks" OR the sender is sasl authenticated.
1. Modify "smtpd_sender_restrictions". We are adding a check before allowing a normal smtp connection. Allowing hosts in mynetwork, then allowing sasl authenticated too. Then a check for local domain address. If its true - the connection will be rejected. [This steps is for ZCS 7.x and older version only].
su - zimbra zmlocalconfig -e postfix_smtpd_sender_restrictions="reject_unknown_sender_domain, permit_mynetworks, permit_sasl_authenticated, check_sender_access hash:/opt/zimbra/postfix/conf/access_table, permit"
For ZCS 8.x, open the file /opt/zimbra/conf/zmconfigd/smtpd_sender_restrictions.cf and add this line in the bottom and save the file.
%%contains VAR:zimbraServiceEnabled antivirus^ check_sender_access hash:/opt/zimbra/postfix/conf/access_table%%
Remaining steps are same for all versions.
2. Create the file "/opt/zimbra/postfix/conf/access_table" and add your domain(s) to it.
localdomain.com REJECT anotherlocaldomain.com REJECT
You can also put some friendly/non-friendly message. Something like this.
localdomain.com REJECT You're not me! anotherlocaldomain.com REJECT You're not me!
3. Create the hash of "/opt/zimbra/postfix/conf/access_table".
postmap /opt/zimbra/postfix/conf/access_table
4. Restart zmmtactl.
zmmtactl restart
Testing
Make following connection from a non-local host which is not part of mynetworks.
telnet ZCS_server_address 25 mail from: user@localdomain.com rcpt to: user2@localdomain.com
You should get following error at the rcpt command.
554 5.7.1 <user@localdomain.com>: Sender address rejected: You're not me!