|0||CHUNKING, DSN, SIZE, and AUTH extensions are enabled.|
|1||Disable CHUNKING extension (RFC1830.3). Sending large messages will be less efficient. However, some servers work slowly or don't work at all when CHUNKING is used (even though they advertize CHUNKING in the list of supported extensions). For instance, disabling CHUNKING may help with MS Exchange servers which have SMTP Tar Pitting enabled.|
|2||Disable Delivery Status Notification extension (RFC1891). DeliveryNotification settings will be ignored.|
|4||Disable SIZE extension (RFC1870). Exceeding maximum allowed message size will not be detected until the message data is completely sent to the server.|
|8||Completely disable ESMTP and send HELO command instead of EHLO as initial greeting. No ESMTP extensions (including PIPELINING) will be available. GetExtensions method will return a null reference (Nothing in Visual Basic). ESMTP authentication will not work (POP-before-SMTP authentication will still work if it's supported by the server).|
Even if ESMTP extensions are enabled, MailBee will use only those extensions which are supported by a particular ESMTP server. The flags provided by this enumeration should be used if the developer wishes to disable certain ESMTP extensions even if they are supported by the server.
8BITMIME/BINARYMIME ESMTP extensions are disabled by default and cannot be enabled via this enumeration's flags. This is because 8BITMIME/BINARYMIME, when used, cause problems with delivery of e-mail messages via multiple SMTP servers in chain. This happens when MailBee submits a message to 8BITMIME/BINARYMIME-enabled SMTP relay server and that server then attempts to relay the message to the end recipient's SMTP server and that destination SMTP server does not support 8BITMIME/BINARYMIME.
To enable 8BITMIME/BINARYMIME (if it's required for some reason), set Conversion8BitTo7bit property to non-default value.
|ESMTP PIPELINING extension can be disabled by setting SmtpServer.Pipelining property value to false. Or, for direct send mode (via DNS MX lookup), the property to set is Smtp.DirectSendDefaults.SmtpOptions.|
To disable all extended features (except AUTH) and achieve maximum compatibility level, set Global.SafeMode to true prior to creating any instances of MailBee classes or calling their methods.