business communication computer connection
Photo by Pixabay on


It is crucial to have good email reputation of your MTA IPs otherwise you could have bad experience in delivering emails to external recipients.

IP warm up is a terminology which helps to inform internet that you are a good sender and they shouldn’t block you because emails are coming from a a new public IP. IP warm-up doesn’t have any full-proof way to build ip reputation but gradually based on email volume, type of emails, email content, your reputation will be built.

I have seen that most of the email gateways don’t have any inbuilt mechanism to perform IP warmup and most of the times you would have to make a plan carefully, like send email in low volume and increase the traffic gradually with mix type of emails. Today, I will explain how to do IP wamup using Cisco Email Security appliance. In this scenario I have a running Cisco ESA and I am introducing a new IP. Let’s see how do we build it’s reputation.

IP warm up Schedule: –

These options are specific to Cisco Email Security Appliance but you can use logic of using Seconds field in Date to divide the % of emails on any other email gateway too.

Create an outbound filter to catch random outgoing email based on the Date header to send email based on seconds value. Create necessary Interface on cisco then use below steps for warm up :

  • Create a new Outbound Content filter to route email of a particular domain:
      • Create an outbound content filter as below:-
      • Navigate to Mail policies > Outbound content filters > Add filter named IPWarmup
      • Condition: ‘Receiving Listener’ is (Select the one used for outbound email sending)
      • Condition: Header Name ‘Date’ and Header Value contains the value in Regex Field
      • Action: Deliver from IP Interface (select the one with NAT of new IP)
  • Add newly created filter to existing outbound mail policy.
      • Navigate to Outbound Mail Policies under ‘Mail Policies’
      • Select newly created content Filter.

Now make use of below table to replace Regex field as per the plan, I have mentioned 6 weeks plan but it depends on your email volume that reputation could be built soon or later. 


In this table we have listed the way to divide traffic based on second field of received header.

DateFilter of Second Field% going outRegex
Week 1[0-1][0-1]6.5%[0-2][0-9]:[0-5][0-9]:[0-1][0-1]
Week 2 & 3[0-2][0-1]10.0%[0-2][0-9]:[0-5][0-9]:[0-2][0-1]
Week 3 & 4[0-3][0-3]26.7%[0-2][0-9]:[0-5][0-9]:[0-3][0-3]
Week 5[0-4][0-5]50.0%[0-2][0-9]:[0-5][0-9]:[0-4][0-5]
Week 6 onwards[0-5][0-9]100.0%[0-2][0-9]:[0-5][0-9]:[0-5][0-9]

Reputation Monitoring

There isn’t a exact way to know that reputation has been built but you can make an understanding that you have send enough email to internet and worked on soft bounces as well as hard bounces and took corrective actions like slow down email sending those domains etc. now you aren’t getting throttled or no complains are received the email isn’t delivering to spam. 

Please refer this article by me to find email reputation :

Thank you for reading !