Thank you for your post.
If the script runs normally without the interruption from the email client, then it is probable the email client is interfering with FileMaker Pro. Is there a reason why you don't use Apple Mail on your Mac? This does not interfere with FileMaker processing.
Thank you for the response, it is helpful to have my initial belief reinforced. I work at a college and the email client was developed here on-campus many years ago. I don't use this particular client for my mac or pc because it has some limitations for my needs. Nevertheless, 38 of 40 users who will be using the solution I am developing exclusively use the college-developed e-mail client; and although that client is being phased out over the next year, I wanted to ensure that I wouldn't run into a similar problem with a new client.
For me to be using that particular client (rare) and receive an email notification in the middle of a script (even more rare) must have been like winning a testing lottery.