For each email notification, the default subject is [Forum Name] as set in your branding settings + the first line of the body of the email. The [Forum Name] also appears at the head of the email; if you have HTML emails enabled, your logo will appear.
Here is a list of Vanilla's default email notification text:
My Account
New Badge
You earned the {BadgeName} badge.
{BadgeDescriptionText}
Rank changes
Congratulations! You've been promoted to {NameOfRank}
{RankBodyText}
New comments on my activity feed posts
{username} commented on your wall.
{PostText}
New posts on my profile's activity feed
{username} posted on your wall.
{PostText}
Private messages
{username} sent you a message
{PmMessageText}
Posts
My answer is accepted
{username} accepted your answer to a question: {DiscussionName}
New answers on my question
{username} answered your question: {DiscussionName}
Send me a follow-up for my answered questions
We noticed you have at least one answer to your question. Can you visit the community and see if any of the answers resolve your question?
If you see an answer you find helpful, please accept one of the answers.
Notify me when a bookmarked question receives an accepted answer
An answer was accepted on your bookmarked question: {DiscussionName}
An answer was accepted on my question
{username} accepted your answer to your question: {DiscussionName}
Status changes on my ideas
The status has changed for {DiscussionName}
Status changes on ideas I voted on
The status has changed for {DiscussionName}
New comments on my posts
{username} commented on {DiscussionName}
{PostText}
New comments on my bookmarked posts
{username} just added a comment in {DiscussionName}
{PostText}
I am mentioned
{username} mentioned you in {DiscussionName}
{PostText}
New comments on posts I've participated in
{username} just added a comment in {DiscussionName}
{PostText}
Groups
Notify me about new announcements in groups I follow
{username} posted an announcement in {GroupName}
Notify me about new comments on posts in groups I follow
{username} commented on {GroupName}
{PostText}
Notify me about new posts in groups I follow
{username} started a new discussion {GroupName}
{PostText}
Notify me of new or updated events in groups I'm following
New Event: {Event Title}
{EventDetails}
I'm invited to a group
Please join my group: {GroupName}
You’ve been invited to join {GroupName}
My group membership request is approved
Your request to join {GroupName} has been approved.
Knowledge Bases
Notify me about new articles
{username} has posted a new article {ArticleName} in {KbName}
{KbText}
Notify me when articles are updated
{username} has edited the article {ArticleName} in {KbName}
{KbText}