There was a change from 7.4 to 8.x in
SMTP Authentication TLS before Auth disable & enable
Since SME v7.5 the default for SMTP Authentication is requires TLS before Auth to increase security. Where a SME7.4 or earlier server with SMTP & SSMTP authentication enabled has been upgraded, users are now unable to send mail. Users will need to enable TLS or Auto for the Authentication encryption setting in their email clients. Some older email clients and devices do not support TLS.
A fix was released in SME7.5.1 to allow this setting to be disabled (ie revert to SME7.4 functionality). Upgrade to SME7.5.1 before using these commands.
To disable this (AUTH without TLS) & revert to SME7.4 defaults do
config setprop qpsmtpd TlsBeforeAuth 0
signal-event email-update
To change back to the sme7.5 & greater default (AUTH with TLS) do
config setprop qpsmtpd TlsBeforeAuth 1
signal-event email-update
Works as expected, of course, the settings in OOo or LO have to be proper for SME. I highly recommend to change settings back, if you need to use the merge-to-mail feature in OOo or LO.
Thanks for pointing me in the right direction.
stefan