When you are creating a new topic on the group website, you can apply existing hashtags by following these steps on the New Topic page:

1. Click or tap the Add Tag button at the right of the subject line.
2. In the Add Hashtags popup, select the desired hashtags. Be aware that some groups require every topic to include at least one hashtag.
3. Click or tap the Add Hashtags button at the bottom of the popup.

When you are writing an email message to send to the group, you can simply enter hashtags on the subject line. If a hashtag you enter on the subject line does not already exist in the group, and the group allows members to create new hashtags, the hashtag is created.

Note: The system treats uppercase and lowercase letters as the same and will not let anyone create the same hashtag with different capitalization. For example, if you create a hashtag of #Question, the system will not allow you to create another hashtag of #question. If a message is sent with a hashtag of #question in the subject line, the system will change that hashtag to #Question before posting the message.

If you email a new topic to a group that requires hashtags but you do not include any hashtags on the email’s subject line, the system returns the message to you with a delivery failure notification that contains the statement “Messages to this group require at least one hashtag to be specified in the subject.” You must resend your message and include at least one of the required hashtags on the subject line. You can find out what hashtags are available by logging in to Groups.io and checking the group’s website. See Viewing the hashtags in a group. 

Note:

• Hashtags take effect only if they are placed on the first message in a topic, and they will be applied to all messages in the topic.
• It is possible to add a hashtag to an emailed reply by editing the subject line, but this addition has no effect. The hashtag will be included in the reply’s subject line for members receiving messages through email, but it will not be included in the subject line of the archived message or of any other messages within the topic.
• Some hashtags might be reserved for moderator use only.
• The hashtag limit is five per topic. (The system allows message subject lines to contain more than five hashtags, but only the first five hashtags are saved in the message archive.)