- iRedMail version (check /etc/iredmail-release): 0.9.9
- Deployed with iRedMail Easy or the downloadable installer? Downloadable Installer
- Linux/BSD distribution name and version: Ubuntu Server 18.04 LTS
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? No
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
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I've just configured iRedMail on an Ubuntu VM and it appears to be working well (sending & receiving ok to internal and external accounts) however when I set up my account on "Outlook" on my MAC (Mac OS Catalina) and "Mail" on my iPhone I can receive e-mail but am unable to send.

In Outlook on my MAC, if I use my server FQDN as the SMTP outgoing server name, I receive the error message "connection to the server failed or was dropped" If I use my server IP address as the SMTP outgoing server name, I receive the same message. I have SSL ON and I've tried ports 576 and 465 both of which are enabled through my network firewall.

In Mail on my iPhone, using my server FQDN as the outgoing server, with SSL ON, I receive the error "cannot connect to the outgoing mail server for "mail.mydomain.com" (replaced for privacy).

I'm a bit of an enthusiast but not an expert in this field by any means, so any assistance to help me solve this issue would be greatly appreciated (please be patient and excuse any "stupid" noob questions).

*EDIT/UPDATE 2019_11_15: after reviewing more posts on the forum I dug into the firewall settings on my mail server and found port 576 did not appear to be open. I added a rule to the IPTABLES file and since then have been able to send and receive mail through Outlook on my Mac. However, I an still unable to get the "Mail" app on my iPhone to work, I can receive mail but still not send, however I am now presented with the error message "Cannot Send Mail the server rejected one of the recipient's addresses. The message has been placed in your Outbox"

*EDIT/UPDATE 2019_11_15: Managed to resolve issue with sending messages from "MAIL" on iPhone. Found that by adding username and password to outgoing mail server settings I was up and running. Not sure why this is required on iOS "MAIL" app and not "OUTLOOK" but there you go.

ADMIN - feel free to leave this post up for benefit of other NOOB's who experience same or similar issues or remove as you see fit.