Issue Summary

Batching notification job takes a really long time due to performance issues with sending emails itself. Jira tries to connect to the SMTP server for every sent message which isn't an optimal solution (~95% of job's time is spent on this). 

Steps to Reproduce

Create a lots of updates and wait for batching job to run.

Expected Results

Jira is able to process email messages in reasonable time.

Actual Results

Jira spends a lot of time on sending email messages which can lead to other problems.

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available