emailing logs

I'm trying to set up E-MAil logs on the FVS338.

Years ago this already worked successfully.

E-Mail Server: securesmtp.t-online.de

Custom SMTP Port: 587

E-Mail User account from ISP: t-online

I have ticked "Login Plain" entering username and password from ISP t-online.

I have ticked "Respond to Identd from SMTP Server.

The FVS338 ist installed directly behind a FRITZBOX 7490. The fritzbox is connected to the VDSL Line.

Basically there is a DMZ between the FRITZBOX 7490 and the FVS338 but with now additional devices connected to it.

FVS338 Firmware: 3.1.1-08 (Latest version)

IP Address Fritzbox 7490: 192.168.2.1

Gateway address in FVS338: 192.168.2.1

Satic IP Address from FVS338: 192.168.2.109

LAN TCP/IP Setup: IP Address: 192.168.100.109 in FVS338

DHCP Server in FVS338 is enabled.

Using FVS338 Diagnostics, it can resolve the SMTP-server securesmtp.t-online.de.

Ping on resolved IP-Addresses is working fine.

Checking the SMTP-server login data using the FRITZBOX 7490 is successful ( I'm receiving Mails from the Push service of the Fritzbox 7490)

Checking SMTP-Server settings using Microsoft Outlook / POP3 is successful as well.

All internet applications are working excellent.

When Trying to send Logs via E-MAil (Menu: "Firewall Logs & EMail/View Log/"SendLog") , the router responds with "Connection interrupted"

No e-Mails are sent out or received by my E-Mail provider.

My Question:

What is wrong in my FVS338 Settings ?

Is there a possibility to check the communication problem of the FVS338 with the SECURSSMTP.t-online.de ? ( I do not see any log-entry in the Log data)

I would be glad if someone could help me.

Best Regards

Ralf