flags verifiedimportantWritten by the Hub

Seven choices that are not numbers are packed here, and the mapping was measured on the stand by setting one switch at a time and reading the column after each save: bit 0 (1) timeout_means_delivered, bit 1 (2) lost_means_delivered, bit 3 (8) prefer_idle_connections, bit 5 (32) greylisted_src_ip, bit 6 (64) greylisted_dst_ip, bit 7 (128) retry_bind_errors. Bits 2 and 4 together carry the three-way intro_error: 4 is "proceed to the next MX", 16 is "report a failure", both clear is "respect the reply code". In every pair the bit set to one is the strict or the affirmative option — strict greylisting, a timeout counted as a delivery, a bind error worth retrying. The field is eight bits wide stored in a signed integer column, so anything with bit 7 set reads back negative: -128 is retry_bind_errors alone, -1 is all eight bits set. flags alone does not say what is configured — it is read together with meaningful, which says which bits were set deliberately. A bit that is off in meaningful inherits from the built-in defaults no matter what flags holds, which is why a freshly created profile is 0 / 0 and changes nothing. That is also the safe value for Hub to write.