The Tumblr platform limits the use of HTML and links in post replies, Ask questions and Fan Mail. If you have a question regarding a particular post, you can send a message to the post author using the post Reply feature, if the author has enabled the feature for the post. However, if you want to include a URL in the question, you must type the URL as plain text. The URL will not be linked to the source. As a workaround, you can reblog the post to ask the original post author a question and include a hyperlinked URL in your query.

Ask Feature

The Ask feature must be enabled by the blog owner before users can send Ask messages to the blogger. If the feature is enabled, an “Ask” or “Ask Me Anything” link will be displayed on the blog owner's profile page. Click the link, then type your message and include the URL text, if desired, in the New Message box. Ask messages do not support hyperlinks. You can choose to send your question to the post author anonymously or as a private message. If you send the message anonymously, the question and answer will be posted to the blog owner’s public blog. If you send the message privately, only you and the blog owner will see the message. You can access and answer your Ask messages by clicking the “Envelope” icon in the top toolbar of your dashboard to open your Tumblr Inbox.

Fan Mail

Followers of your blogs can send Fan Mail messages to you. Users must be following a blog for 48 hours or more to message the blog owner. Fan Mail, like Ask Messages, can be viewed and answered in your Inbox. Like Ask messages, Fan Mail messages do not support HTML or hyperlinks. You can cite a URL in a Fan Mail message, but the URL will appear as text to the recipient. To send a Fan Mail message, click the ”Envelope” icon to open your Tumblr Inbox, then click the “Send Fan Mail” icon open the New Fan Mail Message form. Type a message, include the text URL and click “Send” to send the message. Fan Mail messages are private between you and the recipient.

Reply

If the original post author has enabled Replies for the post, you can click the “Reply” icon to open the Reply dialog box. Type your question in the text box. Type out the URL for the source to reference. The URL will display to the recipient as plain text. Click “Reply” to post the reply. The Reply displays in the blog author’s Notes section, and is publicly viewable.

Reblog

Many Tumblr users post questions and reply to posts by reblogging the original post and appending their questions and comments. When you reblog a post, you can include a question with a hyperlink. The original author is notified that her original post has been reblogged and can reply to the reblog to answer your question. Click the “Reblog” icon at the bottom of the post to open the Reblog form. The original post is cited with a hyperlink if the post is long. Click the arrow next to the "Aa" icon, then click “Text” to display the text of the original post. Type your question at the bottom of the original post. Include a hyperlink, if desired, then click “Reblog Post” to publish the post.