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SMTP Direct Sender Settings

Mail ConnectorsMail SendersSMTP Direct Sender → Settings tab

The SMTP Direct Settings tab lets you set how VPOP3 will send mail using SMTP Direct

DNS Servers to Use

This setting tells VPOP3 the IP addresses of the DNS servers it should use to find the recipients' mail servers. Separate multiple addresses with commas.

If you leave this blank, then VPOP3 will use the DNS servers set in the Misc Settings.

Ideally, VPOP3 should be using local caching DNS servers. DNS servers in some routers are not very good, so if you have a local DNS server, we recommend you use that. Windows Server editions come with a DNS server, another good DNS server for Windows is SimpleDNS. Bind for Windows is also good, but is more complex to configure. Alternatively, for light usage, you could use Google's DNS public servers on and

Edit DNS Overrides

DNS overrides let you 'fake' DNS entries for certain domains. For instance, if you want most of your mail to be sent using MX direct, but mail to * to go through your Internet provider's SMTP relay server, you could add an entry like

This will make VPOP3 find '' when it looks for the MX servers for ''

If your ISP requires SMTP authentication, or a different port number you can specify these as well by modifying the server name as below. Use:

<username>:<password>@<server name>:<port>

eg, you could have

Also, you can use wildcards in the domain name part of the line - eg *

VPOP3 v6.2 and later

In VPOP3 v6.2, you can specify multiple lines which match the target domain, VPOP3 will treat those all as having the same priority

VPOP3 v6.3 and later

Starting in VPOP3 v6.3 you can add more options into the DNS overrides. The first two parts of each line in the overrides is as before - recipient domain, and target mail server, but after that you can specify qualifiers & options

  1. Set priority of the target server - specify $priority:<number>. If you don't specify a priority, then the priority '10' is used.
  2. Check message size - specify $size<operator><number>. If the message size matches the condition, then this line matches
  3. Check message retries - specify $retries<operator><number>. If the number of retries of this message matches the condition, then this line matches
  4. Stop processing the overrides - specify $end. VPOP3 will stop processing the overrides at that point if the recipient domain (and qualifiers, if any) matches.

If a $size and $retries are both specified, then both must match

The <operator> value for the $size and $retries qualifiers are <>, <, =, >, >= and ⇐. Spaces must not surround the operator

So, an example line may be:

  • $retries>=4 $end

This would tell VPOP3 to send the message to your ISP's SMTP server if a message has already had at least 4 retries

DNS Cache Size

This option tells VPOP3 how many recent DNS results it should cache internally. VPOP3 will remember up to this many recent DNS results, but it will also honour the DNS result 'Time to live' (TTL) setting, so entries may be removed from the cache even when the cache isn't full.

If the DNS Servers which VPOP3 is using are local DNS servers with their own caches, then you should usually set VPOP3's own DNS cache size to a small number.

MX Sending Threads

This value tells VPOP3 how many messages it should send at once. 10 is a good starting number. If you set it too high, then throughput will be limited because of the large number of simultaneous connections. If you set it too low, then there will be wasted time as VPOP3 is doing DNS lookups and connecting to remote servers and is not sending messages.

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