Unable to send emails, but can receive just fine

[Starcross]

I have Roundcube installed through Hestia on my Oracle Free Tier server and I am struggling to send an email successfully to my gmail account. I have opened all ports relevant to smtp and am sending it to a valid gmail address. Also, I can receive emails from that gmail address just fine. When I send an email on Roundcube webmail, it says "message sent successfully" but no email address ever receives the message and I eventually get emails back saying that the message sending timed out. Any help so that I can figure out how to send emails would be greatly appreciated. I use Ubuntu Server 22.04.1 LTS. (I don't know what other info is helpful to provide)

[JohnDoh]

The fact Roundcube says "message sent successfully" suggests this is not a Roundcube issue. What do your SMTP server logs show? Have you used a tool like https://www.mail-tester.com/ to test your SMTP server setup for thinks like SPK and DKIM issues?

[blueaquan]

Message delivery to gmail can fail due to multiple reasons, most often it's due to missing SPF, DKIM and DMARC records relating to your domain.  If these records are not in place, you will almost always immediately get a non delivery report (NDR) in your inbox. If your records are in place and still mail delivery is not happening, check whether your mail has gone to the SPAM folder in Gmail.  A proper PTR record could correct that issue permanently. If all the above are in place, then you may have to look at your MTA logs. If you are using Postfix, check /var/log/maillog to investigate further.