Outgoing Email Issue

I have been using a motion detection application for the past five or six years that is setup to send an email with one or two .jpeg attachments when motion is detected to a cell phone (the cell phone receives these as SMS/MMS text messages) and to a gmail and yahoo account. As cox email security has changed thru the years this application was changed to reflect those changes with the latest being TLS and port 587. Every thing was working fine until about a week ago, the cell phone and the yahoo and gmail accounts started not getting all of the messages with the attachments. Got a message from cox to update the profile and change the password on the cox account that was used to send those messages with attachments, made those changes and I also changed the password for that cox account on the application. Since the changes were made to update that cox account, the sending of the emails with the attachments always indicated that the email was sent but the cell phone never receives those messages and the yahoo and gmail accounts receives them only once in awhile. I than conducted tests by using cox web mail to send emails with .jpeg attachments to the cell phone, to the yahoo and gmail accounts, the messages show as being sent and are also in the sent folder of the cox account used for this test. The cell phone never receives those test messages, the yahoo account did not receive the messages and the gmail account only received one out of two that were sent. I just did another test using a different cox account, same results.