diff --git a/Dockerfile b/Dockerfile
index a1e92d5..aa221c3 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -2,5 +2,8 @@ FROM php:apache
 LABEL maintainer="Luke Tainton <luke@tainton.uk>"
 COPY --chown=www-data:www-data hesk /srv
 COPY vhost.conf /etc/apache2/sites-enabled/000-default.conf
-RUN docker-php-ext-install mysqli imap
-RUN a2enmod rewrite
+RUN apt-get update && \
+    apt-get install -y libc-client-dev libkrb5-dev && \
+    docker-php-ext-configure imap --with-kerberos --with-imap-ssl && \
+    docker-php-ext-install mysqli imap && \
+    a2enmod rewrite