@sap-cloud-sdk/mail-client: Allow OnPremise MAIL destinations without basic authentication so that no user and password is required #5136
Description
Is your feature request related to a problem? Please describe.
OnPremise mail servers might not need any authentication. But with the check in mail-client/src/mail-client.ts#L82 it is currently mandatory to provice a user and password by setting the MAIL destination to the Authentication type BasicAuthentication and maintaining User and Password.
Describe the solution you'd like
At least for destination of Proxy Type OnPremise the @sap-cloud-sdk/mail-client should allow destinations where Authentication is set to NoAuthentication.
Describe alternatives you've considered
The configuration of the internal mailserver can't be changed quickly.
Impact / Priority
Affected development phase: Production
Impact: Impaired
Additional context
Same customer as in #5015 is impacted.