Hello

I have just installed a postfix server into a virtual machine on my PC but I can not configure it to send emails to my work email through the company mail server.

Installed OS: Oracle linux 8.0
Vm: Vmware Esxi 6.5, running on a windows PC
Postfix-3.3.1-8.el8.x86_64

Initially I received the error below when I attempted to send a mail;

send-mail: warning: /etc/postfix/main.cf, line 340: overriding earlier entry: relayhost=[****.ne.jp.]:465
postdrop: warning: /etc/postfix/main.cf, line 340: overriding earlier entry: relayhost=[****.ne.jp.]:465


After editing the configuration file,when I run the mailq command after attempting to send a mail, I see the following error message;

5F63D30A7F30 430 Tue Sep 24 11:58:59 root@localdomain.com
(unknown mail transport error).

I am confused because I am thinking the above error has to do with email aliases but I have not set any.

I have read that I need to correctly edit the "relayhost" portion of the main.cf file but I dont know what I am doing wrong as I am new to this.

Any help in plain English with regards to this problem will be appreciated.

Thank you in advance.

...which would indicate that you had TWO relayhost entries in main.cf at the time
What changes did you make?
Why would you think that, when the error message clearly says "unknown mail transport"?

Seems like there's something wrong with your current relayhost setting, whatever it might be.
Here's a document explaining the "relayhost=" setting in more detail.

I noticed that the setting you changed specified TCP port 465. That's SMTPS (SMTP over SSL), which is actually deprecated. It wasn't supported in earlier versions of Postfix, and may still not be (I haven't kept up with the development of Postfix).

See if by any chance your ISP supports delivery via authenticated SMTP (possibly with TLS) via port 587. That's the current standard that most everybody uses, and it's of course supported by Postfix. If they do not and you're forced to use SMTPS on port 465, do a Google search for how to configure Postfix with stunneld. The latter is a separate application (that you'll probably have to install) for general SSL communication.

Hello Ser

Thank you for taking the time to comment on this post.

As you rightly pointed out, my configuration of the postfix server "relayhost" portion was wrong.
Following the link you sent to me, I was able to rightly configure the server to send and receive internal and external emails.

And this is the THIRD THREAD on this same subject, including one 14 year old necropost:
https://www.linuxquestions.org/quest...on-4175661190/
https://www.linuxquestions.org/quest...-1-5-a-341155/

Read the LQ Rules about posting the same question multiple times.

1 members found this post helpful.

What search terms did you use to obtain those? I find that when I search for prior posts I either get nothing (too specific, I guess) or I get a slew of hits that have little to do with the situation I'm trying to resolve (obviously not specific enough). Is there a good LQ page that offers suggestions on how best to get search results that aren't "nothing" or "darned near the whole forum"?

This thread is probably not good place to continue any discussion so redirect as necessary. I'll bet others would join me in a "TIA".

I suspect TB0ne used "Find more posts by..." on the link of the OPs username. They only have 4 posts, and three of them appear to be about how to configure postfix.

1 members found this post helpful.

Ah... that those links to posts came from the OP wasn't clear. Bad. Bad, OP.

2 members found this post helpful.