Mail rendering error in filter subscription email with Microsoft exchange account and Mail.ru

Description

When JIRA sends a filter subscription email to an user with a Microsoft Exchange mail account, the issue status field is not rendered correctly and renders HTML markup in the email.

Step to Reproduce

1. Configure an outgoing mail server
2. Create a filter
3. A user with a Microsoft Exchange mail account subscribes to the filter
4. Wait for JIRA to send the filter subscription mail
5. Open mail with outlook or online browser OWA

Expected result

Actual Result

Filter subscription email is only broken for specific affected mail servers (e.g. exchance, mail.ru), other mail servers like gmail are unaffected.

Workaround

• Change the email format from HTML to Text.
• Check if the affected mail server has advanced settings that allow you to configure HTML rendering, and see if settings can be tweaked to avoid modifying or simplifying the HTML source in such a way that it breaks.

Notes

• JIRA 6.4.x filter subscription mails don't exibit this bug
• Problem seems to be related to the way the different mail servers try to simplify some complex html tags in the email source for rendering.
  Update
• Similar issue is reproducible with mail.ru