[Exim] Should there be any reason for this?

I currently run Exim 4.30 on my linux server and recently starting using
SMTP Auth to allow fellow users to send email when on the road. Everything
is fine apart from a delay when connecting to the mail server. One of the
users reports this problem every time he sends mail thru my mail server.
Both he and I are on DSL connections.

To quote his words in a recent email:

    The test still took a while... It says 'Connecting', 'Connected',
waits
    for ages, 'Sending' and finally 'Sent'... :)   (I never even saw
    'Authorising')

However, when retrieving mail, it is nearly instant for him and other users.
Both the POP & SMTP authentication use the same MySQL table.

Here is the authentication section of my exim.conf file.

begin authenticators

plain_login:
        driver = plaintext
        public_name = PLAIN
        server_condition = ${lookup mysql{SELECT '1' FROM users WHERE
username \
        = '${quote_mysql:$2}' AND cpassword = '${quote_mysql:$3}'}
{yes}{no}}
        server_set_id = $2

fixed_login:
        driver = plaintext
        public_name = LOGIN
        server_prompts = "Username:: : Password::"
        server_condition = ${lookup mysql{SELECT '1' FROM users WHERE
username \
        = '${quote_mysql:$1}' AND cpassword = '${quote_mysql:$2}'}
{yes}{no}}
        server_set_id = $1

fixed_cram:
        driver = cram_md5
        public_name = CRAM-MD5
        server_secret = ${lookup mysql{select password from users where \
        username='${quote_mysql{$1}}'}{$value}fail}
        server_set_id = $1

Any help / information on this 'delay' would be most grateful. By the way,
he uses Outlook Express.

Many thanks,

Stuart O'Reilly
Aurora Solutions

(e) stuart@???