504 5.7.4 Unrecognized authentication type - error when using Office 365 smtp relay

This error message is caused by a mismatch of the SMTP relay server requirements for TLS and the setting in MultiSendcon. When you encounter this error message or are trying to connect to Office 365 SMTP servers smtp.office365.com please switch the SSL setting in the MultiSendcon configuration for this account to "explicit SSL/TLS".

Attention: This option was introduced in v2.10 of MultiSendcon. If you are using an older version you can just download and over-install the new version and the make the configuration change.