How it works . . .

Alligate was designed from the ground up to protect mail servers from all types of SMTP attacks and abuses. Using a unique combination of techniques, Alligate can stop spammers and abusers literally before they attempt to send an actual message.

After installing Alligate it becomes your public facing SMTP server. As soon as a connection request is received, Alligate gets to work and attempts to identify the intent of the sender. Alligate performs various checks and throws various roadblocks into the process at each step in the SMTP transaction. We give the spammer every opportunity to go away on their own. Years of study and experience in this area enables us to identify spammer tactics and actually use their own tactics against them.

Mail servers are designed to accept and process incoming email and are inherently friendly to remote mail servers. Anti-spam and other defenses are generally minimal, or expensive add-ons requiring high annual subscriptions.

Alligate passes allowable traffic to your real mail server instantly and rejects the rest. One Alligate installation can handle traffic for several downstream mail servers making it a great choice for small ISPs, colleges and universities, and government agencies. It's low price makes it a great choice for small businesses too.
I along with others do depend on your product out in front of our mail servers to handle the brunt of the email onslaughts we encounter and I, for one, couldn’t function without Alligate.
- Tony - System Administrator and Alligate User

Enterprise grade defenses to protect against SMTP abuse

Unlimited Domains

Alligate can handle email traffic for any number of domains and domain aliases. Additionally, you can specify any number of downstream mail servers. This allows an installation at one location to handle email traffic for Mali servers located anywhere onsite or off.

Alligate is capable of handling high volumes of traffic with a very low CPU load. It uses several internal caching mechanisms to help reduce off-site connections for DNS, RDNS, blacklists, recipient validation, and other lookup functions for fast and efficient operation.


Alligate uses an extremely effective proprietary form of tarpitting to “discourage” spammers and attempt to get them to disconnect on their own. Unlike other implementations, Alligate uses tarpitting in a totally dynamic way. Depending on the message and sender, tarpitting delays can be inserted at any point in the SMTP transaction and for varying amounts of time. This means that it will be unlikely that legitimate senders will ever be affected negatively, while still imposing tarpit delays where they are most effective.


Greylisting is an extremely effective way to discourage automated spammers. If Alligate does not recognize a sender, and it meets a defined criteria, Alligate will issue a temporary error requesting the sender to try later. Within a few minutes, legitimate senders will try again, but most spammers will not. While several other products have implemented Greylisting as a spam defense, only Alligate lets you specify rules that are used to determine when to enforce Greylisting

Intelligent Throttling

Alligate monitors incoming connections using a user definable subnet mask and looks for unusual activity. Using internal caching mechanisms, it will throttle connections using dynamic tarpitting and eventually blacklist the source temporarily if activity continues. This has proven to be a highly effective way to get removed from spam lists as your server appears to be problematic. Spammers can not afford to wast time on problematic servers and will frequently scrub them from their lists.

Progressive Penalties

Internal scoring techniques allow Alligate to use a progressive penalty system to assess penalties and act at any point in the transaction. This saves valuable bandwidth as many messages can be rejected before the transaction is finished.

In some cases, Alligate may decide that injecting tarpit delays between commands is the most effective way to deal with a potential spammer. It's intelligent algorithms are very effective in rejecting spam while not causing false positives.

Whitelists & Blacklists

Multiple kinds of whitelists and blacklists are maintained internally and also as static, user defined lists.

Alligate also supports external DNSBL and DNSWL services as well as it's own proprietary sender reputation system.

Geolocation is also integrated to all administrators to block (or allow) traffic from selected countries.

RDNS and DNS Blacklists

Each connection is subject to additional tests to try to determine the senders legitimacy factor. The results of these checks become part of the decision tree and can trigger additional actions like adding tarpit seconds, or can help us determine whether or not we want to subject the sender to greylisting and/or other testing mechanisms.


A full suite of utilities is included for backup, migration, folder cleanup, system health monitoring, watchdog services, local recipient validation and much more.

Graphic UI's are provided for load monitoring, real-time connection detail monitoring, and configuration.

Gateway Features

Extensive routing control.
Downstream load balancing.
Failover options for backup or redundant mail servers support.
Fully scalable with high availability cluster support.
Transparent, automatic recipient validation.
SMTP authentication.
Secondary AUTH only port (587) support.
Multiple domain support and alias domain translation.

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