Outlook 2016 For Mac Connection To The Server Failed Or Was Dropped

Hi,

Outlook 2016 For Mac Connection To The Server Failed Or Was Dropped On Fire

I have a new client that we transfered and is getting an Error 17895 'Connection to the server failed or was dropped' on both his MACs and is using Outlook 2011 (same error on Mac Mail). No matter what we check, he cannot send email through our server. I have other clients with MACs that work fine. It's just that there are 2 of them with the same error message.

Mar 24, 2010 Version: 2008 Operating System: Mac OS X 10.5 (Leopard) Processor: Intel Email Client: pop Ever since I updated Entourage 2008 about a week or so ago, I've been getting intermittent errors (off and on all day - twenty and more times- when automatically retrieving email: Connection to the server failed or was dropped. Car tuning software for mac. Could not retrieve mail. Feb 07, 2018  Our Pune Address A 101, Gera Park View, Pune, Maharashtra - 411014, India. Call Us USA: +1 888 900 4529 UK: +44 800 088 5522.

Here's my setup and what we've done;
ME Enter. 7.58, Win 2008 R2, valid certificate, ports 993 and 587 both with SSL.
- all users were not able to send at all through our server. We checked, their fixed IP was blacklisted. Had the IP removed from the blacklist
- iPhones (IOS) are now able to send without problems, MACs still getting -17895 error. Added their IP to our whitelist and allowed to relay. Still same error.
- In the ME Systray, I see their IP show up in SMTP IN, but no activity.
- checked Antivirus and Firewall on the MAC, no AV and FW is inactive.
- not listed in any DENY file in config.
- changed Outlook to try port 25, still can't send, changed back to 587.
- changed outgoing server to a backup server we use with less security (used only for web services locally sent), added the IP to allow relay, same error msg.

- restarted SMTP service, same.
- check Google, most of the information leads nowhere.

Outlook 2016 For Mac Connection To The Server Failed Or Was Dropped On Top

- ran fix/scan on the Outlook database, no change.
- did a telnet on port 587 and 25, connects.
- a MAC tech checked out the MAC, can't find a problem.
I'm literally at my wit's end. Has anyone had this problem before, or what do I seem to be missing?
Any help would be appreciated.
Thanks,
Karl