Can't find application menu button so I can't block by subject

The provider I use for my landline is a very small company with no time or budget for fixing some of their own problems. As a result, I get a few email messages every day containing "Storage limit exceeded" as the subject. I spoke to the vendor, and they don't know what causes the message to fire. They also confirmed that I have never come close to exceeding my storage limit. I can't mark the sender as a spam account, because they occasionally send me legitimate correspondence. I did a little research, and it looks like Thunderbird will allow me to filter by subject. If that works as I suspect it might, that would allow me to filter out the unwanted messages and still receive other communications from this vendor. I went to the following page: https://support.mozilla.org/en-US/kb/organize-your-messages-using-filters#w_create-a-new-filter Under Create a New Filter, the instructions say: Click the Application menu button and then Tools followed by Message Filters. The problem for me is that no such Application menu button (three horizontal lines) appears anywhere in my Thunderbird display, unless it's hidden really well. The most I can do at the moment is Click the Settings icon, which allows me to drill down to Privacy & Security. From there, it's unclear how I should proceed. I guess my first question is, does the absence of an application menu button mean there's something wrong with my Thunderbird installation, or is that linked instruction page simply out of date? The second question is, can I use my current interface to block incoming email based on subject instead of sender, and if so, how do I do that? Thanks.