Block size MTA option

Message size MTA options:  (integer &#x3e; 0)
The MTA measures message size in units of MTA "blocks". For instance, the MTA message transaction log file (resulting from placing the   option on a channel) records message  sizes in terms of blocks. MTA blocks are also the unit of measurement for various message size limit and message size based effects, as specified via channel options including ,  ,   ,  ,   ,  ,   , and  , and via MTA options including  ,   ,  ,  ,  ,  ,   ,  ,   , and   , and via LDAP attributes named by MTA options including    ,  ,    ,   , and  , and the alias option. Normally an MTA block is equivalent to 1024 octets. This option can be used to modify this sense of what a block is.

NOTE: The MTA stores message sizes internally as an integer number of blocks. If the size of a block in bytes is set to a very small value it is possible for a very large message to cause an integer overflow. A message size of greater than 2&#x2a;&#x2a;31 blocks would be needed, but this value is not inconceivable if the block size is small enough.

Given the extensive list (above) of values measured in units of "blocks", it may be useful here to also list values that are not measured in "blocks". In particular, measurements that do not use the, but which instead are always measured in units of bytes, include the  conversion channel environment variable  , the Content-length: MIME header line value, the SMTP protocol extension SIZE value (see RFC 1870), and the user-level   LDAP attribute (more properly from the MTA&#x27;s point of view, the attribute pointed to by the   MTA option) and the  domain-level   LDAP attribute (which note is not used by the MTA proper). Furthermore, the user-level  LDAP attribute (more properly from the MTA&#x27;s point of view, the attribute pointed to by the   MTA option) and the  Sieve filter   test&#x27;s  value are also normally interpreted as bytes, (though Sieve   values can optionally use a K, M, or G unit indicator to indicator measuring in units of 2&#x2a;&#x2a;10, 2&#x2a;&#x2a;20, or 2&#x2a;&#x2a;30, and similarly the   attribute&#x27;s value can use K, M, or G unit indicators).

See also:
 * Message size MTA options
 * logging Option
 * blocklimit Option
 * sourceblocklimit Option
 * alternateblocklimit Option
 * holdlimit Option
 * nonurgentblocklimit Option
 * normalblocklimit Option
 * urgentblocklimit Option
 * maxblocks Option
 * block_limit MTA Option
 * bounce_block_limit MTA Option
 * content_return_block_limit MTA Option
 * header_limit MTA Option
 * log_size_bins MTA Option
 * non_urgent_block_limit MTA Option
 * normal_block_limit MTA Option
 * urgent_block_limit MTA Option
 * max_header_block_use MTA Option
 * max_internal_blocks MTA Option
 * ldap_sourceblocklimit MTA Option
 * ldap_blocklimit MTA Option
 * ldap_maximum_message_size MTA Option
 * ldap_domain_attr_sourceblocklimit MTA Option
 * ldap_domain_attr_blocklimit MTA Option
 * alias_blocklimit Option
 * MTA transaction log entry format