Hi @giridhar0813,
Welcome to the 
community support forums !!
We are excited that you joined our OSS community. Please read about some of the FAQs in the community 
This seems to be not related to Loki but a general issue with the configuration. You can do a basic verification by simply testing the above configuration via telnet command.
In your helm chart, please define the SMTP port as well.
You can have a look at this reference post to see what other SMTP settings are required to make it work correctly.
Let us know if this helps.