I have a new email server (postfix/dovecot/mysql) with accounts
migrated from another server (different platform) and email addresses
with ampersands like "r&d@domain.com" that worked on my old email
server are not working now.

I'd like some help tracking this issue down.

Can anyone tell me if this looks like a postfix, dovecot or mysql issue?

Some log info follows. For brevity I'm just posting this log snip as
I'm thinking I will get a simple answer to this but I will be happy to
post postfix, dovecot or mysql settings in detail if they are required.

Thank you, Brad

dovecot.log file: [...] dovecot: Mar 27 16:37:23 Info: auth(default): auth(?,216.111.149.248):
Invalid username: r&d@domain.com dovecot: Mar 27 16:37:23 Info: auth(default): cram-md5(?, 216.111.149.248): Username contains disallowed character: 0x26 dovecot: Mar 27 16:37:24 Info: auth(default): new auth connection:
pid=68420 dovecot: Mar 27 16:37:25 Info: auth(default): client out: FAIL 1 dovecot: Mar 27 16:37:25 Info: auth(default): client in: AUTH 2 [....] dovecot: Mar 27 16:37:25 Info: auth(default): auth(?,216.111.149.248):
Invalid username: r&d@domain.com dovecot: Mar 27 16:37:25 Info: auth(default): plain(?, 216.111.149.248): Username contains disallowed character: 0x26 dovecot: Mar 27 16:37:27 Info: auth(default): client out: FAIL 2 dovecot: Mar 27 16:37:27 Info: imap-login: Disconnected (auth failed,
2 attempts): method=PLAIN, rip=216.111.149.248, lip=216.111.149.248,
secured [...]