Apache James 队列落后

由于某种原因，当传递的消息总是落后于实际发送时，我经常遇到队列释放问题。James 设置为将传入消息发送到网关 (Postfix)。

RemoteDelivery 类具有：

        // Set it to try to deliver (in a separate thread) immediately
        // (triggered by storage)

究竟什么是“存储”以及在哪里配置？

我设置了一个 mailet，它将匹配的消息（基于收件人域）发送到网关（在 mailetcontainer 中指定）。在它被“卡住”以传送到网关之前，这一直很好。在 James 日志中，它显示为Successfully spooled mail来自发件人，然后显示为

[TID=83] INFO  11:04:54,858 | james.smtpserver | Id='1510412390' User='' Successfully spooled mail Mail1581005094857-978ba32f-74e6-4ca1-b903-7994637a9873 from <address@remote> on <remote sender IP> for [<address@local>]
...
[TID=734] INFO  11:04:55,290 | james.mailetcontext | Remotely delivering mail Mail1581005094857-978ba32f-74e6-4ca1-b903-7994637a9873
[TID=34] INFO  11:04:55,290 | james.mailetcontext | Remote delivery thread (0) will process mail Mail1581005072858-90055113-03cf-4bc0-84d7-d47d176feef2
[TID=34] INFO  11:04:55,290 | james.mailetcontext | Attempting to deliver Mail1581005072858-90055113-03cf-4bc0-84d7-d47d176feef2
[TID=734] INFO  11:04:55,312 | james.mailetcontext | Adding SMTP gateway: <gateway address>
[TID=734] INFO  11:04:55,312 | james.mailetcontext | Sending mail to [<address@local>] via [<gateway address>]
[TID=34] INFO  11:04:55,312 | james.mailetcontext | Adding SMTP gateway: <gateway adrdress>
[TID=34] INFO  11:04:55,312 | james.mailetcontext | Attempting delivery of Mail1581005072858-90055113-03cf-4bc0-84d7-d47d176feef2 to host <gateway adrdress> at <gateway adrdress> from <address@remote> for addresses [<address@local>]]

但我没有看到邮件已成功发送到网关。

为了让它“解开”，我需要将另一条传入消息发送给 James，该消息将命中同一个 mailet 以推送之前被卡住的假脱机消息。然后在詹姆斯日志中它将显示为

[TID=35] INFO  11:22:14,443 | james.mailetcontext | Mail (Mail1581005094857-978ba32f-74e6-4ca1-b903-7994637a9873) sent successfully to <gateway adrdress> at <gateway adrdress> from <address@remote> for [[<address@local>]]

看起来，如果中继主机发生变化，相关队列就会开始表现不同，就像一个纸巾管，里面有乒乓球。只有当足够多的球被推入时，才能从另一端取出一个。对此有什么想法吗？