`banner`: `` ('default =' `ESMTP Proxmox`):: ESMTP banner. `before_queue_filtering`: `` ('default =' `0`):: Enable before queue filtering by pmg-smtp-filter `conn_count_limit`: ` (0 - N)` ('default =' `50`):: How many simultaneous connections any client is allowed to make to this service. To disable this feature, specify a limit of 0. `conn_rate_limit`: ` (0 - N)` ('default =' `0`):: The maximal number of connection attempts any client is allowed to make to this service per minute. To disable this feature, specify a limit of 0. `dnsbl_sites`: `` :: Optional list of DNS white/blacklist domains (see postscreen_dnsbl_sites parameter). `dnsbl_threshold`: ` (0 - N)` ('default =' `1`):: The inclusive lower bound for blocking a remote SMTP client, based on its combined DNSBL score (see postscreen_dnsbl_threshold parameter). `dwarning`: ` (0 - N)` ('default =' `4`):: SMTP delay warning time (in hours). `greylist`: `` ('default =' `1`):: Use Greylisting for IPv4. `greylist6`: `` ('default =' `0`):: Use Greylisting for IPv6. `greylistmask4`: ` (0 - 32)` ('default =' `24`):: Netmask to apply for greylisting IPv4 hosts `greylistmask6`: ` (0 - 128)` ('default =' `64`):: Netmask to apply for greylisting IPv6 hosts `helotests`: `` ('default =' `0`):: Use SMTP HELO tests. `hide_received`: `` ('default =' `0`):: Hide received header in outgoing mails. `maxsize`: ` (1024 - N)` ('default =' `10485760`):: Maximum email size. Larger mails are rejected. `message_rate_limit`: ` (0 - N)` ('default =' `0`):: The maximal number of message delivery requests that any client is allowed to make to this service per minute.To disable this feature, specify a limit of 0. `ndr_on_block`: `` ('default =' `0`):: Send out NDR when mail gets blocked `rejectunknown`: `` ('default =' `0`):: Reject unknown clients. `rejectunknownsender`: `` ('default =' `0`):: Reject unknown senders. `spf`: `` ('default =' `1`):: Use Sender Policy Framework. `verifyreceivers`: `<450 | 550>` :: Enable receiver verification. The value spefifies the numerical reply code when the Postfix SMTP server rejects a recipient address.