iRedMail/cubemail not sending to certain domains.

So, I set up an iRedMail, Postfix SMTP, Dovecot IMAP, Nginx, MariaDB, Amavised-new, SpamAssassin, ClamAV, Roundcube, and iRedAPD Postfix policy server for greylisting (which I removed). All on Ubuntu 18.04 server.

Everything works fine when sending out through roundcube to emails such as gmail, etc – though it detects it as spam, and it receives mail fine as well to gmail.

The main problem is it will not deliver mail to other emails of friends on other domains or receive it (friend@somedomain.com). It returns the following error when sending out from cubemail:

friend@somedomain.com: host mail.somedomain.com[ip.add.ress] said: 550-Verification failed for test@mymailserver.com 550-No Such User Here 550 Sender verify failed (in reply to RCPT TO command)

My friend receives the following error when trying to send me an email to the mailserver:

test@mymailserver.com No Such User Here

Reporting-MTA: dns; webhost.com Action: failed Final-Recipient: rfc822;test@mymailserver.com Status: 5.0.0

mymailserver.com is the email I’m sending from to friend@somedomain.com and it doesn’t go through, and vise versa, even though I know the email exists. It also will not send to forwards he has that point to his friend@somedomain.com account.

/var/log/mail.log displays the same error and is of no help.

Here is how my machine and his machine are configured just for clarity.

mymailserver.com MX records point mail.mymailserver.com to another ip outside of the server its domain is hosted on. There are, however, no mx records on mymailserver.com as it doesn’t have domains pointing to it via DNS servers to handle it for hosting sites, etc.

somedomain.com is by itself at its webhosting company and has many forwarded aliases to the friend account, which are reached through other emails, just not any from mymailserver.com, and he cannot send any to test@mymailserver.com.

All I’m trying to do is have my mail for a certain domain whose website is hosted on a different server, to handle its mail on a different server, thus leaving its web address alone, etc. I seem to be missing something that is not allowing other domains to recognize it, yet gmail has no problems.

What could be the problem here? Any help is appreciated.