Using Send E-mail from Administration -> System -> Mail:

1. if message type is Text, it's this known bug JRA-35145, so expected
2. if message type is HTML, the content of the email is wrongly formatted (no paragraph):
   • Input message:

     Jira is a commercial software product that can be licensed for running on-premises or available as a hosted application. Pricing depends on the maximum number of users, typically $50 per user for in-house and $7 per month per user for the hosted version.[6]

     Atlassian provides Jira for free to open source projects meeting certain criteria, and to organizations that are non-profit, non-government, non-academic, non-commercial, non-political, and secular.

     For academic and commercial customers, the full source code is available under a developer source license.[6]

     Starting with Jira 4, a ten-user starter license costs $10 with all proceeds benefiting Room to Read.[7] Starter licenses are also available for other Atlassian products that can integrate with Jira, such as Bonfire, Confluence, Crucible, GreenHopper, Bamboo, FishEye and Crowd.[8]

   • Email content: