Match SASL username and From address in Zimbra SMTP

Zimbra uses postfix as its MTA. Postifix default configurations have some weakness which we have to modify get optimum performance and fight against spam.

Firstly, postfix has a trusted network [mynetwork] from which users can send mails without verifying their username and password.

Later on if we impose SMTP authentication for sending mails the users the users can still send mails by changing their from address [It is usually happens when a user is compromised]. A reference log is given below for better understanding.


Dec 17 14:17:45 mail postfix/submission/smtpd[8055]: 62B2A7009F9: client=unknown[x.x.x.x], sasl_method=LOGIN, sasl_username=user
Dec 17 14:17:45 mail postfix/qmgr[29613]: 62B2A7009F9: from=<gks@example.com>, size=5705, nrcpt=3 (queue active)


So, we are still in some security holes with our mail server. To be more strict we can match the from address of the user with the username that he uses in SMTP authentication. Let's see how to do that.


Login to Zimbra shell:
su zimbra

Run below command:
zmprov mcf zimbraMtaSmtpdSenderLoginMaps  proxy:ldap:/opt/zimbra/conf/ldap-slm.cf +zimbraMtaSmtpdSenderRestrictions reject_authenticated_sender_login_mismatch

Edit the file /opt/zimbra/conf/zmconfigd/smtpd_sender_restrictions.cf  as below:
permit_mynetworks, reject_sender_login_mismatch

Restart zimbra service [Not required actually because Zimbra will automatically apply this after one miniute]:
zmcontrol restart

Now if one of your accounts is compromised, it is not possible to send SPAM mails using different from address which will help you find out the compromised ID easily.

PHP module "mod_rewrite" enable in cPanel

Cpanel is a widely used application for Web and Domain hosting solution. Providers use cPanel & WHM to provide virtual private or dedicated servers for hosting. Web developers worldwide uses URL Rewriting for web sites.

Last time I faced a issue with "mod_rewrite" module of PHP in my shared cPanel hosting server. Later the solution came with following modification.


I have added following lines in a .htaccess file and upload in public_html folder of created user of cPanel.

<IfModule mod_rewrite.c>
DirectoryIndex index.php
RewriteEngine on

RewriteCond $1 !^(index\.php|assets|robots\.txt|favicon\.ico)
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ ./index.php/$1 [L,QSA]
</IfModule>

Zimbra Troubleshooting: A network service error has occurred

Sometimes we face a problem with Zimbra webmail interface. If a user wants to login in his webmail it shows "A network service error has occurred". Though its a temporary problem but users became confused and starts feeling unwell about his email service.

By default Zimbra uses DoSFilter Throttling Mechanism to avoid large number of request over a short period of time. So if the Zimbra server see requests more than safe amount from an specific IP address / user that will be throttled and the user may face the mentioned error.

The attribute by which we have to add the safe IP address in Zimbra is "zimbraHttpThrottleSafeIPs". It does not have a default value, however these following IP addresses are whitelisted by default.

1) 127.0.0.1
2) ::1
3) 0:0:0:0:0:0:0:1
4) All mailboxd servers

To add more IP addresses in whitelist please do the following.

Login to Shell >> su zimbra >> zmprov mcf +zimbraHttpThrottleSafeIPs 192.168.2.1 >> zmmailboxdctl restart