pine/alpine need a patch to read maildir mailboxes; the package on FreeBSD does not offer this patch.
In /usr/ports/mail/alpine do a make patch.
Change to work directory and apply the patch from ~on/Alpine-2.20/maildir.patch.
The patch fails to install the files maildir.h and maildir.c in the proper directory imap/c-client/, you have to do that by hand.
Change to alpine-2.20 directory and run configure with the needed options, you must at least disable SSL (--without-ssl), other options like IPv6, kerberos, tcl are not needed either. I used:
./configure --without-ipv6 --without-tcl --without-ldap --without-krb5 --without-ssl
make and install by hand.