Dreaded Taxes

After we signed the documents and put them in the envelopes, Selena agreed to take them to the post office. It was April 15th, and we were making sure our taxes were post marked that day. Selena took extra care to make sure she had more than enough postage on the envelope and put it in the mailbox. Unfortunately, the postage way the only part of the envelope that Selena double-checked. She walked away from the mailbox and suddenly a sense of dread rushed over her.

Was the envelope even addressed?