DOT is a Mailutils filter useful for POP3 and SMTP I/O. In encode mode, it "byte-stuffs" the input by outputting an additional '.' in front of any '.' appearing at the beginning of a line. Upon closing the filter in this mode, it outputs additional ".\n".
When decoding, the reverse is performed: additional dots are removed from beginning of lines. A single dot on a line by itself (i.e. the sequence "\n.\n") marks the end of the stream and causes the filter to return EOF.
Mailutils also provides a hairy version of this filter, called CRLFDOT, which combines its functionality with that of the CRLF filter, i.e. performs the CRLF/LF translation in addition to byte-stuffing.
The following object, declared in mailutils/filter.h describes the DOT filter:
extern mu_filter_record_t mu_dot_filter;
This filter does not take arguments.
The example below shows how to create a DOT filter instance in decode mode for reading:
int rc; /* Return code */ mu_stream_t flt; /* Filter stream */ mu_stream_t input; /* Input stream */ initialize_input_stream (&input); rc = mu_filter_create (&flt, input, "dot", MU_FILTER_DECODE, MU_STREAM_READ);