Text is sent only after a numeric status response line has been sent that indicates that text will follow. Text is sent as a series of successive lines of textual matter, each terminated with CR-LF pair. A single line containing only a period (.) is sent to indicate the end of the text (i.e., the server will send a CR-LF pair at the end of the last line of text, a period, and another CR-LF pair).
If the text contained a period as the first character of the text line in the original, that first period is doubled. Therefore, the client must examine the first character of each line received, and for those beginning with a period, determine either that this is the end of the text or whether to collapse the doubled period to a single one.
The intention is that text messages will usually be displayed on the user's terminal whereas command/status responses will be interpreted by the client program before any possible display is done.