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Subject : AV-codes in archives
Target : All users
Date : 02-22-93
Rev. : 1.00 / 02-22/93
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Currently the following programs can create a AV-code that MTA can
detect:
- PKZIP (from 1.xx to the current release);
- ARJ (from 2.xx to the current release);
- SQZ (from 10.83 and up );
You can use the KeepAV, KeepAVNoCode, IncludeAVFiles and ExcludeAVFiles
options to work with AV-codes (they are described in MTADOCEN.DOC in
great detail). You should observe the following problems which have
NOTHING to do with MTA but with the way AV-codes are handled by the
developers of PKZIP, ARJ and SQZ:
- SQZ has a rather large AV-user field (the comment part of the field)
but in most cases MTA can extract ALL information from the archive;
- ARJ has a small (as designed) problem. ARJ 2.39b (the second beta for
ARJ 2.40 and the current release at the date of this document) will
send a message to the users that any AV-code from a release previous
to 2.39b is OBSOLETE. MTA can work in the old fashion as with ARJ
2.39a and previous releases, because ARJ 2.39b will still reveal the
AV-code and AV-user (description part);
- PKZIP must be watched very carefully. Files with a AV-code created by
PKZIP 1.10 or lower will show the correct AV-code when you work with
PKZIP 1.10 but won't show the AV-code when you work with PKZIP 1,93a,
2.04c/d/g. This is how PKWare designed their new AV-code. It is done
because the old PKZIP 1.1x AV-code is hacked. The same goes the other
way around. PKZIP 2.xx archives with an AV-code will not show the
AV-code when handled with PKZIP 1.1x (in most cases the files won't
be extracted either because PKZIP 1.xx is not upward compatible with
PKZIP 2.xx archives, only backward). When you use a mix of PKZIP 1.xx
and PKZIP 2.xx AV-code files (which will be the case for a few months
between the conversion from PKZIP 1.xx to PKZIP 2.xx), you should set
the KeepAVNoCode option in MTA. MTA is always able to DETECT that a
PKZIP (whatever release) is created with an AV-code, but MTA is
unable (because PKZIP is unable) to extract AV-codes from BOTH
formats with ONE program. With this option set, MTA will always keep
AV-codes from both PKZIP 1.xx and PKZIP 2.xx formatted files !
With PKZIP 2.xx files (as with SQZ), MTA will try to obtain as much
information as possible, so extended comments in the AV-code (the
comment-part) are extracted.