One of the reliability feature provided by BizTalk adapters is configurable Retry. BizTalk allows you to configure the parameters like Number of Retry, Retry interval.
BizTalk detects, if there is any failure while sending data using adapters like FTP, HTTP, SMTP…. and then attempts to send data again as per the Retry parameters configured.
If data transfer fails even after all Retry attempts then it will log an error in Event log, after which manual intervention required to detect the problem