Postfix TLS配置客户端证书的潜在问题咨询

我最近查阅Postfix官方文档时，看到关于客户端证书参数smtp_tls_cert_file的说明：

smtp_tls_cert_file (default: empty)

[...]

Do not configure client certificates unless you must present client TLS certificates to one or more servers. Client certificates are not usually needed, and can cause problems in configurations that work well without them. The recommended setting is to let the defaults stand:

(note this is for smtp_tls_cert_file not smtpd).

文档里那句“can cause problems in configurations that work well without them”说得太模糊了，我想请教下，配置客户端证书和密钥文件可能会导致哪些具体问题？

另外附上一个可能的配置示例（在main.cf中）：

smtp_tls_cert_file=$smtpd_tls_cert_file
smtp_tls_key_file=$smtpd_tls_key_file

备注：内容来源于stack exchange，提问作者hjsimpson