A communication apparatus capable of notifying a receiver of a reception mail error or transmission mail error by printing or the like and preventing incorrect data or error notification mail from being transferred or stored without notifying the user of the error, and a control method and storage medium therefor. To accomplish this, when analysis of electronic mail data reveals a MIME analysis error, BASE64 decoding error, TIFF analysis error, or image decoding error, i.e., when data which cannot be handled by the communication apparatus is contained, a global variable FORWARD is set to “1”. Also, when the received electronic mail is an error notification mail, the variable FORWARD is set to “1”. When the variable FORWARD is set to “1”, transfer and BOX storage of the received mail are inhibited, and the mail is printed by a printer section (2). When the variable FORWARD is not set to “1”, the received mail is transferred to the designated transfer destination or stored by BOX storage.