i have a problem sending my mails. It’s Gmail IMAP 993 and SMTP 587.
when i sent an email an error eccours. “Connection failed” SMTP is not reachable.
so i change it manually to “USE SSL/TLS if available” and it works.
but i tried all different securitymodes. in general settings and it Always happens again. and i do have to change it manually again after trying to send an email.
Those are the default settings, that work. If it doesn’t work with those settings for you, then possibly something is interfering with your connection.
As a test, can you completely disable any anti-virus, firewall, proxy or VPN, then try send again. Sometimes even restarting your router may resolve this.