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# OpenSSL Version Mismatches

Your system may have multiple versions of OpenSSL on it. it is possible that some libraries which Cyrus can use might be linked against different versions of the OpenSSL libraries, or that those may be different from the version which Cyrus itself will use.

Major updates of OpenSSL are not always compatible with each other at the API level. OpenSSL is used by many libraries and system components and not all of those become compatible with the new version at the same time. Because of this some Linux distributions choose to ship multiple OpenSSL versions and allow components to use whichever version is appropriate.

If two different versions of the OpenSSL libraries linked into one program, it results in program instability. To check if this is happening, look for warnings from the linker like the following:

    /usr/bin/ld: warning: libssl.so.10, needed by /usr/lib/gcc/x86_64-redhat-linux/7/../../../../lib64/libclamav.so, may conflict with libssl.so.1.1
    /usr/bin/ld: warning: libcrypto.so.10, needed by /usr/lib/gcc/x86_64-redhat-linux/7/../../../../lib64/libclamav.so, may conflict with libcrypto.so.1.1

In this case, ClamAV is still linked against OpenSSL 1.0, while Cyrus is building with OpenSSL 1.1.

# Libical v1.0.1 or v2.0

You may see warnings regarding libical v2.0 being recommended to support certain functionality. Currently libical v1.0.1 is sufficient, unless you need/want RSCALE (non-gregorian recurrences), VPOLL (consensus scheduling), or VAVAILABILITY (specifying availability over time) functionality. If v2 is required, it will need to be installed from github.