Off the wall ... come now. I'll walk you through the wonderful world of criminal law:
First let's start with the relevant parts of the statute:
One might well construct the argument for a crime here along the lines you mention. It appears though that you were citing from paragraph (2)(a), which is the crime of counterfeiting. The crime, of forgery is found in paragraph (2)(d) but is pretty similar. The Indiana Courts lay out the elements of forgery as follows:
To convict Bocanegra of forgery, the State was required to prove beyond a reasonable doubt that (1) Bocanegra, (2) with intent to defraud, (3) made, uttered, or possessed a written instrument in such a manner that it purported to have been made (a) by another person (b) at another time (c) with different provisions or (d) by authority of one who did not give authority. Ind.Code § 35–43–5–2.
Proof of intent to defraud requires a showing the defendant demonstrated “intent to deceive and thereby work a reliance and injury.” Wendling v. State, 465 N.E.2d 169, 170 (Ind.1984) (emphasis added). Actual injury is not required; potential injury is enough. See Diallo v. State, 928 N.E.2d 250, 252 (Ind.Ct.App.2010) (“[T]here must be a potential benefit to the maker or potential injury to the defrauded party”) (quoting Jacobs v. State, 640 N.E.2d 61, 65 (Ind.Ct.App.1994) (emphasis added)).
Bocanegra v. State, 969 N.E.2d 1026, 1028 (Ind. Ct. App. 2012). The case law makes it clear that the forgery does not have to purport to be from a real person. It simply has to purport to be from someone other than the person who created it. The courts make clear that the real thrust of the crime is the intent to defraud; i.e. the intent to deceive and "thereby work a reliance and injury." There is no question here that the e-mail purported to be from someone else and that there was an intent to deceive. So it seem to be the issue would come down to whether there was the intent to work an injury — for the OP to gain some potential benefit from the employer or to cause a potential injury to the employer.
And prosecutors do get creative. Consider a case involving a federal wire fraud charge prosecution of a federal employee who was paid a salary (rather than by the hour) and who was alleged to have falsified his hours worked with his employer. He allegedly did not work all the hours he claimed to have worked. The employee argued for dismissal of the charge saying that because he was paid a salary his pay would not have been any different had he reported the real (reduced) hours he worked. He then said this meant that the government suffered no injury because was not out any extra money from the falsified hours. But the court agreed with the U.S. Attorney and rejected the motion to dismiss stating:
Had Mr. Ransom accurately recorded the number of hours he actually worked during the course of a pay period and failed to account with leave for all of his absent time, HUD would have had the opportunity to exercise its right to terminate Mr. Ransom’s employment if it so chose. But it was deprived of valuable information about Mr. Ransom’s work habits by virtue of his false reports. Therefore, regardless of whether the submission of falsified T & A Reports impacted the amount Mr. Ransom received in any given paycheck, it did help permit Mr. Ransom to continue his employment despite his reduced work hours and to continue to receive a paycheck. Therefore, if the government can establish the requisite intent at trial, the submission of the Reports could be said to have resulted in a deprivation of something of value to the
United States—namely, the amount paid Mr. Ransom in salary—by means of deceit.
United States v. Ransom, Case No. 09-20057-JWL, Memorandum and Order 11/9/2009 (D. Kansas). In short, the court bought the argument that by deceiving the employer into continuing to employ him rather than getting fired had he accurately reported his hours, the agency was injured by keeping him employed and paying his salary after the deception.
Continued employment might constitute the injury in the case of the OP, too. Whether the Indiana courts would go down the same path the federal district court did to determine that as an injury I cannot say, but if a federal court judge bought it, so might a state court judge.