Problems sending emails via SMTP PORT 25

[CRM-BE]

Hello,
I'm having problems sending emails in version 9.1.2.

The settings are:
SMTP, Security=None, Port=25, Auth=LOGIN

(The mail server is a local-server)

Error message:
######################
Message:
Email sending error: Unable to connect with STARTTLS: stream_socket_enable_crypto(): SSL operation failed with code 1. OpenSSL Error messages:
error:0A000086:SSL routines::certificate verify failed

Code:
0

Exception Class:
Symfony\Component\Mailer\Exception\TransportExcept ion

File:
/var/www/html/espocrm/vendor/symfony/mailer/Transport/Smtp/Stream/SocketStream.php

Line:
171
#######################

Apparently STARTSSL is required - Why?

[lazovic]

Hi CRM-BE,

Have you tried using STARTTLS or SSL/TLS protocols in your email account settings in EspoCRM? Maybe you should try other ports?

[CRM-BE]

Everything was fine before the update.
Port 25 should remain without SSL if possible.

[Vadym]

Hi CRM-BE,

To ensure secure and reliable email delivery, try to configure your email client to use the following SMTP settings:

• SMTP server: [your.smtp.server.com]
• Port: 587
• Security: STARTTLS (TLS)
• Authentication: Required (use your full email address and password)

Port 587 is the industry-recommended standard for sending email securely and is supported by all modern email applications.
If you are currently using a different port (like 25 or 465), we recommend switching to port 587 with TLS to avoid delivery issues and ensure encryption.