STARTTLS error

Hello,

Qmail
Courier IMAP

One of our Customer's has a friend who gets the following bounceback
when they try to send mail to him (our Customer):

----- CUT HERE -----
The following address(es) failed:

user@domain.tld
SMTP error from remote mailer after STARTTLS: host mail.domain.tld
[123.45.67.89]:
454 TLS not available: missing certificate (#4.3.0):
retry timeout exceeded
----- CUT HERE -----

The bounceback comes from the sender's mail server.

I believe our Qmail did have the TLS patch applied, but I recompiled,
making sure that it was not included this time, however, the
Customer's friend still gets the bounce-back.

The only other thing I could think of was TLS in Courier-IMAP, but as
far as I know, that does not have anything to do with the ability to
receive mail from another mail server?

Any light you can shed on this would be greatly appreciated.

Sincerely,

Alan Murrell <swasak@hotmail.com>