Users unable to send personal emails on wifi. Disabling Transparent port 465 and 587 allows some, but not all users to send emails.

Question

Good Morning Everyone, 
 Almost a year ago my company ended up moving to a new building. In that process we ended up purchasing a second UTM9 firewall. When the migration to the new building was completed, we ended up using the new firewall and still have the old firewall as a spare. 
 During the transition time we ended up losing our IT manager and hired on a new one. The Old manager did the configuration of the old firewall and the new manager did the configuration for the new one. I have a PDF of the old firewall configuration if that might help. 
 Once we got settled in a large number of users came to me telling me they couldn't send email from their personal emails anymore and would get an error message "The connection to the outgoing server 'smtp.xxxxxxx.com' failed." At the time the new manager wouldn't let me troubleshoot, but now I am given more leeway to look into this. 
 So I'm following rule 1, and checking the logs as i replicate this issue. In the SMTP log I see this below 
 2020:04:01-10:47:57 206 exim-in[21713]: 2020-04-01 10:47:57 SMTP connection from ([10.0.50.43]) [10.0.50.43]:57649 lost 
 2020:04:01-10:48:06 206 exim-in[6472]: 2020-04-01 10:48:06 SMTP connection from [10.0.50.43]:57650 (TCP/IP connection count = 1) 
 
 I don't see anything in the firewall log, or any of the other logs mentioned in Rule 1. The email I am trying to send does not show up in the mail manager either which I guess is to be expected since it can't even connect to the mail server. 
 
 Interestingly if I disable transparent mode port 465 my email will go through. However if I disable the ports for 587 and 25 domain mail stops making it to the firewall for some reason. 
 
 When I examine the configuration of the old firewall, I don't see anything really standing out as to what would cause this. 
 
 I am not certain that this is necessarily the firewall's problem, but I know disabling the Transparent Port on 465 allows my email on wifi to connect so this may at least point me to the problem. 
 
 One last thing, if a user configures their personal email on the Outlook phone app, their email works fine. But some users are stubborn and would rather just turn their wifi off and I would REALLY like to know why this is. 
 
 Thank you for your help! 
 
 Regards, 
 
 Tyler