Your message entitled “[Rails] PDF writing” was sent in reply to a
message with a different subject. You probably intended to start a
new thread; however, your mailer, like most MUAs, outsmarted you by
including a References: header field.
Therefore, your message is still threaded under the original subject,
instead of your new subject. Unfortunately, this can cause your
message to get lost in a completely unrelated thread!
In the future, if you’d like to start a new thread, please compose a
NEW message to firstname.lastname@example.org
Thank you for your time and consideration…