Historically in Zimbra it has been possible to log in using the account email address, but also using an email alias. For security reasons it is recommended to disable the log in by use of an alias. Follow below steps to find out if alias login is enabled on your Zimbra deployment, and configure it […]
Tag Archives | email security
SMTP Smuggling in Zimbra Postfix a technical deepdive
E-mail providers like Microsoft Exchange Online and GMX allowed to pass <LF>.<CR><LF> sequence unfiltered from their outbound (sending mails) SMTP server to the inbound (receiving mails) SMTP server (postfix in our case). In the case of Postfix serving as an outbound/inbound (sending mails/receiving mails) server, it does not ignore the sequence ‘<LF>.<CR><LF>’; rather, it interprets […]
What are the benefits of using Zimbra OpenSSL in FIPS mode?
If you installed or upgraded to Zimbra version 9.0.0.P34, 8.8.15.P41, 10.0.2 or higher, Zimbra will use OpenSSL 3.0.x and FIPS compliance for OpenSSL will be enabled by default. To check if your Zimbra OpenSSL is using FIPS you can run the following command, that should fail with Error setting digest: /opt/zimbra/common/bin/openssl md5 /dev/null There are […]
Sending incoming email with bad headers to Junk
Email is always evolving and recently Gmail has started to reject email with bad headers for some customers. Rejecting email with bad headers may help protect against DKIM replay attacks (more on replay attacks in an upcoming blog). When we are talking about messages with bad headers, we mean messages that are not compliant with […]
New phishing attacks may use .zip, .mov and other new Internet domains
Beware of fraudulent activities using the newly launched .zip and .mov top-level domains. Phishing attacks have already targeted well-known brands like Microsoft and Okta. Apart from phishing, the new .zip and .mov TLDs have also been used for various malicious purposes like hosting zip bombs, redirecting to YouTube videos, and offering file compression services. Here […]
A Milter for using Spamhaus HBL with Zimbra Postfix
In this article you will learn how to use Spamhaus Hash Blocklist (HBL) to improve email protection in Zimbra. For a long time administrators of Zimbra have relied on Spamhaus to fight incoming spam by configuring Postfix using traditional blacklists. These traditional blocklists work by blocking IP (ranges) and domains of known spammers. When an […]