When sending bulk emails from Options & Settings -> Send email, vertical white space is ignored in the body of the message. So something like:

Dear all,

Jira will be down for maintatenance

Yours, Jira-admin

Ends up as: Dear all, Jira will be down for maintenance Yours, Jira-admin.

It would be nice if we could send basic plaintext messages, or even better had a good UI for sending HTML mark-up.