Thank you for taking the time to reply. I have removed the /usr/local/lib64/c-client dir (indeed, I have re-compiled php+alpine in the past on this box). However, I'm afraid exactly the same error message came back when I tried to recompile PHP.
I've checked the config.log, and I now wonder if that error message is misleading:
Code:
</snip>
configure:41317: checking for IMAP support
configure:41353: result: yes
configure:41362: checking for IMAP Kerberos support
configure:41377: result: no
configure:41386: checking for IMAP SSL support
configure:41401: result: /usr
conftest.c:373:10: fatal error: /mail.h: No such file or directory
#include </mail.h>
^~~~~~~~~
compilation terminated.
configure:41759: checking for utf8_mime2text signature
configure:41781: cc -c -I -D_REENTRANT conftest.c >&5
conftest.c:375:10: fatal error: c-client.h: No such file or directory
#include <c-client.h>
^~~~~~~~~~~~
compilation terminated.
configure:41781: $? = 1
configure: failed program was:
| /* confdefs.h */
| #define PACKAGE_NAME ""
</snip>
It kind of looks like the "mail.h: no such file or directory" error happens first.