data_buffer_size
Specified the size of the buffer used to read chunks of the message payload
during the DATA
phase of the SMTP transaction. Making this larger will
improve the throughput in terms of bytes-per-syscall at the expense of
using more RAM.
The default size is 128KB (128 * 1024
). If your average message size is
significantly larger than the default, then you may wish to increase this
value.