Issue Type icon being attached to JIRA issue upon reply to issue notification

Issue summary

In JIRA 7.1.2 Issue Type icons are being added to the issue as an attachment when a user replies to the issue created email notification. This did not occur in JIRA 6.4.13 using same configuration.

Steps to reproduce

1. Create new JIRA instance
2. Configure inbound and outbound mail server
3. Create business project
4. Add Create or Comment mail handler with settings noted below (default settings)
5. Change user profile to notify of own changes
6. Create issue in test project
7. Reply to issue created notification
   • During testing reply sent from Microsoft Outlook
8. Attachment will appear on issue when reply comment is added

Mail handler settings:

Issue Type: Task 
Bulk: ignore
CC Assignee: true
CC Watchers: false
Create Users: false
Notify Users: true
Strip Quotes: false

Expected behavior

Issue type image is not added at attachment. This is the behavior experienced in JIRA 6.4.13 using same mail handler settings.

Note

This issue is related to the Microsoft Outlook client that is being used for replying the notification email from JIRA. It is tested with JIRA 7.x and Gmail to reply the notification email and the reply does not add any attachment.

Workarounds

1. Remove the issue type icon from the email notification, as suggested by rnd42 in this comment. Tested on Jira 7.7
2. Changing the properties of the issue type icon image, as suggested by mriedel1029065643 in this comment.