1 Topic by my.digital.hobbies (edited by my.digital.hobbies 2022-03-02 23:23:43)

  • my.digital.hobbies
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  • Posts: 9

Topic: Issue sending via SMTP SSL

==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 1.5.1 MARIADB edition.
- Deployed with iRedMail Easy or the downloadable installer? yes
- Linux/BSD distribution name and version: CENTOS STREAM 8
- 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.

I'm using an external application to sent emails. Via gmail.com this works 100%, but I want to use an Iredmail account that I created on 1 of the 8 domains that Iredmail is serving.

The email account used works in Iredmail and I can send and receive via a email client. The program requires the following details:
- SMTP server name or IP
- Port 587 or 465
- Account
- Password Account

Tested port 465 as described here (https://www.stevenrombauts.be/2018/12/t … r-openssl/) and I can logon via the cmdline. If I use these settings in the local program (which is not working at the moment), it tells me that it is connected, but than it stops. Replacing the domain name with the (local) IP address of Iredmail does not make a difference.

If I use the local program on port 587 it tells me that no SSL connection was found (STARTTLS).

Checking the logs, I don't see enough details to fingerpoint the issue. For the moment I do want to exclude internet related matters, so server and client are only locally on a private network.

I have added postmaster and dovecot configs in the attached zip.

What could be the next steps to analyze the handshake between client/server ?

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Spider Email Archiver: On-Premises, lightweight email archiving software developed by iRedMail team. Supports Amazon S3 compatible storage and custom branding.

2 Reply by thedethwalker

  • thedethwalker
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Re: Issue sending via SMTP SSL

my.digital.hobbies wrote:

What could be the next steps to analyze the handshake between client/server ?

You should attach a listener on port 587 (between your program and postfix server) and look at the communication between them. You could use something like tcpdump or wireshark. Also while doing so you should look at an active postfix log (use something like "journalctl -f -u postfix.service"). First check if they are able to communicate at all, then check how the communication is going. The problem should be one of the two.

Here is the RFC on STARTTLS: https://datatracker.ietf.org/doc/html/rfc3207
There is an example dialog there (section 5). If your program can issue an EHLO command and a STARTTLS command then its a communication problem. In this case you could check what version of TLS the server and your program are using. If your program cannot connect at all then it is a connection problem.

3 Reply by ZhangHuangbin

  • ZhangHuangbin
  • ZhangHuangbin
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Re: Issue sending via SMTP SSL

Please use port 465 with SSL, or 587 with STARTTLS (or TLS).
if it doesn't work, please extract related log lines from Postfix log lines and paste here so that others can help troubleshoot.