Problem with squirrelmail login

[Mike Bernson]

I had a working squirrel mail in 14.04.

I upgrade to 16.04 and had problem with login. so I moved back to 14.04 and created a free
install of 16.04 and then install squirrelmail. I then copied the config file over to the
new install and got the same problem.

When I try to login in I get a an error from dovecot (the imap server).
Jan 2 11:37:24 mail dovecot: imap-login: Disconnected (no auth attempts in 0 secs): user=<>, rip=192.168.1.169, lip=192.168.2.21, TLS handshaking: SSL_accept() failed: error:14094418:SSL routines:SSL3_READ_BYTES:tlsv1 alert unknown ca: SSL alert number 48, session=<rpyeKh9FmgDAqAGp>

and on squirrelmail i get the follow error:

Error connecting to IMAP server: tls://mail.mlb.org.
0 :

The dovecot server is 14.04.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: squirrelmail 2:1.4.23~svn20120406-2ubuntu1.16.04.1
ProcVersionSignature: Ubuntu 4.4.0-51.72-generic 4.4.30
Uname: Linux 4.4.0-51-generic x86_64
NonfreeKernelModules: xt_multiport nls_utf8 btrfs ufs qnx4 hfsplus hfs minix ntfs msdos jfs xfs ipt_REJECT nf_reject_ipv4 binfmt_misc ebtable_filter ebtables ip6table_filter ip6_tables ipmi_devintf ipmi_si ipmi_msghandler veth mptctl mptbase iptable_filter ip_tables x_tables zfs zunicode zcommon znvpair spl zavl bridge stp llc crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel aes_x86_64 lrw gf128mul glue_helper input_leds ablk_helper cryptd serio_raw amd64_edac_mod edac_mce_amd fam15h_power k10temp shpchp edac_core i2c_piix4 8250_fintek mac_hid kvm_amd kvm irqbypass nfsd auth_rpcgss nfs_acl lockd grace vhost_net vhost macvtap macvlan lp parport sunrpc autofs4 raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear igb dca ptp hid_generic uas usbhid mpt3sas ahci pps_core raid_class psmouse hid usb_storage libahci megaraid_sas i2c_algo_bit scsi_transport_sas fjes
ApportVersion: 2.20.1-0ubuntu2.4
Architecture: amd64
Date: Mon Jan 2 16:32:00 2017
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: squirrelmail
UpgradeStatus: No upgrade log present (probably fresh install)