I've been dealing with a problem when none of emails get delivered. Correction: it looks like this happened after SP4 update. IRead all threads on the Forum, but cant find a solution. Problem: Clicking 'Test' button not sending any emails. No emails for Event notifications/ Missed calls/ Invitations emails sent. No iPhone push notifications. No 'Generate Support Info' email is sent. Brand new clean Debian 8 server install on Digitalocean. No Firewall installed. 3CX Phone System Professional Edition. 3CX Version - 15.0.60903.0 [SP4] - even though i don't remember installing it from 'Updates' menu. I've set up Settings->Email Settings Gmail SMPT exactly as per this article http://www.3cx.com/blog/docs/gmail-mail-server/ After Initial 3CX install - i did receive event notifications and invitation emails. But No 'Test' button emails, and iPhone didn't push notifications were working. But recently (i suppose after SP4 update) no emails at all. I'm suspecting it's something to do with Ports or 3CX security module. SSH checking if ports 443, 587, 2195, 2196 are open: nc -vt xxx.xxx.x.xxx 443 443 (https) : Connection refused 587 (submission) : Connection refused 2195 (?) : Connection refused 2196 (?) : Connection refused 3CX Firewall Check shows all : done but it doesn't check ports 443, 587, 2195, 2196 I will appreciate your advice.