Hyphenated emails not getting through

[embert]

YaBB SE Version: 1.5.5
PHP Version: 4.3.4
MySQL Version: 4.0.x
Server Platform: Unix, Linux, or BSD
Link to Forum: http://www.penny-farthing.net/yabbse/index.php

Problem Description:
I am having trouble receiving any emails (eg notifications, moderator notes and standard emails) generated by YaBB SE when I use a hyphenated email address. Works OK for non-hyphenated addresses.

Is this an issue?

When my forum gets back online, I'll try escaping the hyphens and seeing if that works.

[embert]

Tried sending emails from YaBB SE with hyphens escaped (\) with no success.

[[Unknown]]

Hypenated email address for sender or receiver?

-[Unknown]

[embert]

Hyphenated emails for the receiver.

For example, if I am using the "Email your members" function within the admin mode, the emails do not arrive for those members with hyphenated email addresses.

Also, I am the moderator of all my boards. One of my own email addresses is hyphenated, and when I set that as my personal email address in my "Profile" page I do not receive "Report this to the Moderator" emails from members.

I also have this problem with another PHP-based script (Coppermine Gallery) which also cannot send emails to my hyphenated email address.