mta_source_to_text
mta_relay_to_text(relay), source ? mta_source_to_text(source) : "NULL");
mta_source_to_text(c->source),
mta_source_to_text(c->source),
mta_source_to_text(c->source),
mta_source_to_text(r->src),
mta_source_to_text(block->source),
static const char *mta_source_to_text(struct mta_source *);