Cisco ESA C390 Email Blast - Configure Multiple Connection to Serve Outbound Connection

[Akmal Zamin]

Hi All,
Presently we only setup one connection for email blast. Can anyone please help to assist on how to setup multiple outbound connection? Thanks in advance.

[Mathew Huynh]

Hey there,

Can you please elaborate into what is one connection and the ask for multiple outbound connections?

I am assuming it's listeners... but I just want to make sure.

Thank you,

Mathew

[Akmal Zamin]

Hi Mathew, yes it's listener im talking about.

[Mathew Huynh]

Hey Akmalzamin

Typically you can create as many listeners as you choose - however a listener is tied to an IP interface + port; you can create multiple listeners on same IP but they need to be on different ports if you wanted more listeners for differentiation.

However with one listener setup - your device should be able to send out as many emails as you configured within connection limits.

So what I would like to know is - what is the outcome that is being sought after ?

If your current listener is a public listener where all outgoing emails are being rejected by the RAT - you can rectify this with a RELAYLIST addition in your HAT Table.

If you're just looking to differentiate which listener will accept email for different hosts etc; then you will need to be aware that you'd possibly need more IPs allocated; or more ports open.

Please let us know.

Thanks,

Mathew 

[Akmal Zamin]

For my case, one listener for outgoing mail already setup and working. This time, i want to add one more listener also for outgoing mail. Is this possible to achieve and is there any guide to set this up beside this article(https://www.cisco.com/c/en/us/td/docs/security/esa/esa11-1/user_guide/b_ESA_Admin_Guide_11_1/b_ESA_Admin_Guide_chapter_0100.html)?

[Mathew Huynh]

Hey Akmalzamin,

You can definitely create as many listeners as you please; but remember that it's IP and port bound listeners.

I feel you could always use the existing listener and just add any other relaying (outbound) servers to the existing RELAYLIST to achieve the same result.

The additional listener is only if you want to bind it to a different IP or port.

THanks,

Mathew

[Akmal Zamin]

Hi Mathew, 

Thank for the explanation. Ok let say if I have two departments (A and B) and I want to assign each department with one listener, I just have to makesure each department(listener) have different IP? Am I correct on this one?

And also if I have multiple listener, will my esa(email blast) blast email faster and to more recipients?

[Mathew Huynh]

Hey Akmalzamin,

Thank for the explanation. Ok let say if I have two departments (A and B) and I want to assign each department with one listener, I just have to makesure each department(listener) have different IP? Am I correct on this one?

>> Yes, different IPs on port 25; however my question i would ask would be more of a design aspect now; what's the purpose or outcome of needing different listeners for departments? Would they be sending from different mail server IPs and you want to have strict routing/firewall rules where one department cannot cross into another departments listener? 

And also if I have multiple listener, will my esa(email blast) blast email faster and to more recipients?

>> Not necessarily, as all listeners will fall under this same global connection limits.

So if global limits are set to recommended 300 concurrent; and you set one listener to accept a tcp queue size of 1000 and the other at 500; they will both be kept at 300 at the global setting anyway.

The main concept of multiple listeners is if you are going to be using different IPs for routing emails and need this differentiation for the flow of traffic.

If you simply wanted to allow 1 department more connection limits/size etc over the other; then you can use one listener (where they share the same IP to connect to send emails to) and then separate them via the mail flow policies and sendergroups.

I hope that helps,

Mathew