How to convince gmail to group emails into a thread?

Question

gmail

Hello.
I use zabbix monitoring system at work. I send notifications about events to my gmail.com address using a simple script and read them on my smartphone.
The downside is that gmail doesn't merge related messages into threads. For example, a letter with the subject OK: ping mts gate failed and PROBLEM: ping mts gate failed are not chained together.
What can you do to get gmail to merge the emails in the paragraph above into one thread?
PS I can do almost anything with a letter: sender / recipient / subject / body / headers ...
PPS I send letters using a simple script and the sendemail program

Answer 1

In my case (it was necessary NOT to use chains), I made the subject of the letter unique, but here is what Google gave (just the first random link):
https://support.cloudhq.net/how-does-gmail-decide-...