Как правильно изменить размер элемента структуры

==22524== 88 bytes in 1 blocks are definitely lost in loss record 16 of 32
==22524== at 0x4C244E8: malloc (vg_replace_malloc.c:236)
==22524== by 0x408AC7: set_user_options (pop_pass_x.c:1496)
==22524== by 0x40A12A: pop_pass (pop_pass_x.c:1189)
==22524== by 0x40E88F: qpopper (popper_x.c:354)
==22524== by 0x417446: main (main_x.c:175)

код

struct mailbox_map x_mailbox_map = { NULL, NULL, Null };
...
for ...

if ( x_mailbox_map.domain == NULL )
x_mailbox_map.domain = (char *) malloc ( sizeof ( char * ) * ( strlen ( token != NULL && token [ 0 ] != '\0' ? token : mydomain ) + 1 ) );
else
x_mailbox_map.domain = (char *) realloc ( x_mailbox_map.domain, sizeof ( char * ) * ( strlen ( token != NULL && token [ 0 ] != '\0' ? token : mydomain ) + 1 ) );
x_mailbox_map.domain [ 0 ] = '\0';
strcpy ( x_mailbox_map.domain, token != NULL && token [ 0 ] != '\0' ? token : mydomain );

тока не про *x_mailbox_map.domain = '\0';