User Tools

Site Tools


Mail Sender Advanced Settings

Mail ConnectorsMail Senders → (name) → Advanced


Domain Filtering

For VPOP3 v6.11 and later, see the Domain Filtering section of the user manual.

The Domain Filtering box lets you restrict which email messages are sent via this Mail Sender.

You specify each rule on a separate line, and the message will be sent if it matches any sender rule and any recipient rule. If there are only sender rules or only recipient rules, then messages will be sent if there it matches any of that type of rule.

You can specify either the sender as
From: <wildcard>
e.g. From: * or From:

or the recipient as
<wildcard domain>
e.g. or customerdomain.*

Negate a rule by putting a ! (exclamation mark/bang) in front of it.

So a sample might be

This would use this Mail Sender to send messages from either or AND to either or someone@<something>

Only send messages waiting at start of connection

If this box is checked, then VPOP3 will get a list of messages waiting in the outgoing message queue at the time when the connection starts, and VPOP3 will only send those messages during this connection. After sending (or attempting to send) those messages, VPOP3 will stop sending messages, even if new messages have arrived in in the outqueue.

If this box is not checked, then, once VPOP3 has tried to send all the messages currently in the outqueue, it will check again to see if any new messages have arrived while it was sending those. If there are any new messages, VPOP3 will try to send those, and then check again, and so on, until there are no new messages waiting to be sent.

Send smaller messages first

If this box is checked, then VPOP3 will sort the pending outgoing messages by size and send the smaller messages first.

If this box is not checked, then VPOP3 will try to send messages in order by the time they arrived (First-in First-out - FIFO).

Reverse send order

If this box is checked, then VPOP3 will reverse the order set by the above setting. So, if the Send smaller messages first box is checked, and Reverse send order is checked, VPOP3 will try to send larger messages first, or if the Send smaller messages first box is not checked, VPOP3 will send the most recently queued messages before the older messages (Last-in First-out - LIFO)

Sender Retry

The Sender Retry box tells VPOP3 when to retry any messages which were failed with a temporary error.

With SMTP, the receiving SMTP server or smarthost can refuse to accept a message by returning an error code. There are two types of error:

  • A temporary/transient error. These are indicated by an SMTP error code beginning with a '4'. In this case, the sender should retry later. Some possible situations where this may occur are - the receiving server is too busy, the receiving disk is full, greylisting, etc. Network errors (eg connections dropping or timing out) are also treated as this type of error.
  • A permanent error. These are indicated by an SMTP error code beginning with a '5'. In this case the sender should not retry later. Some possible situations for this may be - sender is not authorised, message is not allowed for some reason, the recipient doesn't exist.

If VPOP3 receives a permanent error, then it will not retry the message, and the sender will receive a delivery failure report from VPOP3 indicating what error VPOP3 received from the onward mail server.

If VPOP3 receives a temporary error, then it will retry according to the Sender Retry & Max Retry times. The Sender Retry setting is a list of comma separated numbers which indicate the minutes between retries. If more retries occur than numbers, then VPOP3 will re-use the last number

So, a Sender Retry setting of '10,30' means that VPOP3 will retry a message 10 minutes after first trying to send it. If that fails as well, then the next attempt will be 30 minutes later, then subsequent retries will be 30 minutes later again, and so on.

It is a good idea to have the first retry or two set to a short delay such as 5 or 10 minutes. This will mean that greylisting does not delay a message too long. It is then a good idea to slow down retries after a while, so that messages which are not going for some reason will not slow down other messages. So, for instance, 10,10,30,60,60,180 could be a sensible retry scheme.

Max Retry Time

The Max Retry Time is how long VPOP3 tries to resend messages which encounter temporary errors before failing them. This should generally be set to 72 hours or so. Sometimes onward mail servers have problems, so if you fail too quickly you may not give the administrators of those servers time to fix their servers before VPOP3 gives up trying to send mail. If you set this too long, then messages may be outdated if they eventually arrive.

Warn after

The Warn after time tells VPOP3 to send a 'warning' message to the sender if a message has not been sent after the specified time. This will inform the sender that the message has not been sent yet, and will indicate the most recent error which VPOP3 has received whilst trying to send that message.


The Timeouts are global (apply to all senders), and tell VPOP3 how long to wait for a response at each stage of an SMTP transaction.

The defaults are shown below, and are taken from the recommended delays in the SMTP standards. There is generally no need to alter these.

reference/sender_advanced_settings.txt · Last modified: 2018/11/14 10:45 (external edit)