diff --git a/cmdeploy/src/cmdeploy/dovecot/dovecot.conf.j2 b/cmdeploy/src/cmdeploy/dovecot/dovecot.conf.j2
index 036bd79f..a7ce7b62 100644
--- a/cmdeploy/src/cmdeploy/dovecot/dovecot.conf.j2
+++ b/cmdeploy/src/cmdeploy/dovecot/dovecot.conf.j2
@@ -7,6 +7,7 @@ listen = 0.0.0.0
 protocols = imap lmtp
 
 auth_mechanisms = plain
+auth_username_chars = abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890.-_@[]
 
 {% if debug == true %}
 auth_verbose = yes