FAQ / Server Products

We are experiencing a delay when sending mail via Hexamail. When we use a telnet session we can see that it takes up to 30 seconds for Hexamail to respond to the MAIL FROM:... command.
Check your DNS based spam blocking lists (SPAMBlocker/Detection/IP), including
SPF and DomainKeys (SPAMBlocker/Detection/Sender)

All of those features make DNS requests just after the Mail from command and can lead to delays if you have large numbers of lists, incoming mail or slow DNS server responses.

Overall you should not worry as its just a latency in each email and should not affect overall throughput as many connections can be processed in parallel.

You should though limit the number of DNS checks you are doing to improve the latency, by choosing only the most effective lists or lists that combine other lists into a single DNS based list.

There are also the following guides: