I use alpine as my primary e-mail client. In order to get it compiled for Solaris 11 (snv_166 and later), you will need to make a few changes to the source.

[paulie@adrenaline ~]$ uname -orv
5.11 snv_166 Solaris
[paulie@adrenaline ~]$ ./configure --with-ssl-include-dir=
/usr/include/openssl
[paulie@adrenaline ~]$ gmake

We run into a problem ...

In file included from osdep.c:66:
scandir.c: In function `Scandir':
scandir.c:45: error: structure has no member named `dd_fd'

Let's investigate:

[paulie@adrenaline ~]$ vi /usr/include/dirent.h
#if defined(__USE_LEGACY_PROTOTYPES__)
/* traditional SVR4 definition */
typedef struct {
        int     dd_fd;          /* file descriptor */
        int     dd_loc;         /* offset in block */
        int     dd_size;        /* amount of valid data */
        char    *dd_buf;        /* directory block */
} DIR;                          /* stream data from opendir()
#else
/* default definition (POSIX conformant) */
typedef struct {
        int     d_fd;           /* file descriptor */
        int     d_loc;          /* offset in block */
        int     d_size;         /* amount of valid data */
        char    *d_buf;         /* directory block */
} DIR;                          /* stream data from opendir()
#endif  /* __USE_LEGACY_PROTOTYPES__ */

Interesting, so alpine *should* be using POSIX instead of the older UNIX SVR4 definitions. Let's make a change to the scandir.c file, which is located in alpine-2.00/imap/c-client/scandir.c. On line 45 I see the following use of dd_fd:

if ((!dirp) || (fstat (dirp->dd_fd,&stb) < 0)) return -1;

Let's change that dd_fd to d_fd.

if ((!dirp) || (fstat (dirp->d_fd,&stb) < 0)) return -1;

After recompile, everything works as expected. I'm sure there is a better way of fixing this problem, but considering how trivial this issue is, a small edit is sufficient.