Install certificates

updated @ 2010-04-16

How to import (self-signed) certificates into the certificate store of your phone if the application doesn't do this for you.

This can be of use if the mail client silently refuses your self-signed certificate (it refuses to continue in the setup wizard where you entered your IMAP credentials with use of SSL for example).

This howto assumes a rooted phone and talks specifically about certificates for mail. These can be substituted for other applications of course. You also need the Android developer toolkit, or more specifically the adb tool. This tutorial assumes it's in your PATH, but you can provide a full path (like /usr/local/bin/android/android-sdk-linux/tools/adb). Also, it works best when performed as root on your pc.

Get the latest bcprov-jdk16-NNN.jar from http://www.bouncycastle.org/latest_releases.html
Get /etc/ssl/certs/dovecot.der from your server (exact location may vary); this is the certificate used by the Dovecot IMAPs server
Similarly, get /etc/exim4/exim.crt from your server; this is for smtp (sending of email)

# install the jar, on my debian/ubuntu box that's this:
sudo mv bcprov-jdk16-145.jar /usr/lib/jvm/java-6-sun-1.6.0.14/jre/lib/ext/

# add the certificate as trusted cert
keytool -importcert -keystore cacerts.bks -storetype BKS -provider org.bouncycastle.jce.provider.BouncyCastleProvider -storepass changeit -trustcacerts -alias YOURSERVER_dovecot -file dovecot.der

# test whether it worked
keytool -keystore cacerts.bks -storetype BKS -provider org.bouncycastle.jce.provider.BouncyCastleProvider -storepass changeit -v -list| grep -i yourserver

# Repeat this for exim.crt:
keytool -importcert -keystore cacerts.bks -storetype BKS -provider org.bouncycastle.jce.provider.BouncyCastleProvider -storepass changeit -trustcacerts -alias YOURSERVER_exim -file exim.crt

# Now upload to the phone. First mount its /system read/write:
adb shell mount -o remount,rw /dev/block/mtdblock3 /system

# Upload the certificates
adb push cacerts.bks /system/etc/security/

# Remount /system read-only
adb shell mount -o remount,ro /dev/block/mtdblock3 /system

Kill Mail on your device or reboot. Setup of your email account should work now.

Based on this comment, but with fixes.