Sending One's Work to Oneself to Copyright--Is this Effective?

Last Wednesday on her blog, Stephanie Faris wrote about four ways for authors to avoid being sued. Among those were copyrighting one's work by sending a copy of the story to oneself.  After I typed the first draft of my memoir, my mom told me to do this before letting anyone else read it.  I'd saved it as pdf file one Sunday afternoon and was about to email it to the members of my book club through our group email.  "Did you copyright it yet?" Mom asked, meaning did I send myself a copy. I hadn't--not yet--so I saved the email I'd begun in my draft folder and the next day sent myself the first copy I'd printed out. I'd just typed a second draft that I'd saved as a pdf. When I received it back three days later, I resumed sending the email, coincidentally just before our monthly meeting in June. Of the members who showed up, only one said she'd gotten it and the others present each admitted that they had not checked their email that day. I also sent it to to a guy I knew in high school that same day.

Below is the envelope I sent the story to myself in with the story still inside (I was told not to open it). The receipt from the postal place is used to cover up  most of my address.

This method is known as the "poor man's copyright," and according to this link, it has proven ineffective.  But even so, my mom said, it still works. Another post quoted in the blog points out that your work is copyrighted once you create it. But I've already mailed my story to myself, so what is done is done.  

For the record, I've only received some feedback as of yet from those to whom I emailed the story.  Though I understand it takes different people different amounts of time to read.  Another person I'd sent it to is the bartender at my favorite local bar. I saw her two weeks ago at a neighborhood grocery store, and she said she'd begun to read my manuscript, but that she's a slow reader.  Another I sent it to, a fellow bar patron was texting me about what she had read so far when she received the email.