A basic IPv6 lab might include just a few routers and switches to emulate a network, a server or two to carry common services like DNS, SMTP, and HTTP plus testing applications, and a few hosts to
IPv6 Online Port Scanner IPv6Scanner is a port scanner that allows you to probe a server for open, closed or filtered ports. You can specify a host name, IPv4 or IPv6 address. IPv4 or IPv6: If green, you will have no problem on World IPv6 day. If this fails, seek help from your IT department, helpdesk, or ISP tech support. If this fails, consider using the full test, with IE, Firefox, Safari, or Chrome, to get more detailed information about possible failure reasons. IPv6: If red or blank, do not stress! test how you send email (//email/test From:) test TLS v1.3 email: we use it in and out, and we can test it in and out; test IPv6 email: we use it in and we can test it in and out; test live SPF, DKIM, DMARC; test live MTA-STS, SMTP TLS Reporting, DANE; test and limit to specific TLS versions, cipher suites, etc. (sender and receiver) test Figure 1: SMTP fall back from IPv6 to IPv4 The receiving server successfully gets the sending server to retry over IPv4, as described in SMTP IPv6 to IPv4 Fallback: An Applicability Statement . Blacklists An IP address is added to a blacklist when the address is verified as a bad site. On this page you can test the ping latency of your internet connection, and compare the performance of your IPv4 and IPv6 connectivity. AAAA records and web IPv6 connectivity (ipv6-test.com) Check your IPv6 Path Maximum Transmission Unit If a host sends IPv6 packets that are too big for part of its route, it should get a Packet Too Big message so it can re-transmit the data in smaller packets. In my case (updown.io) I don't even send email over IPv6, but I monitor other's servers, and if someones configure a simple TCP check on port 25 (to check if his SMTP server is up) I can't do this from DO. I never realized this before but this is pretty bad for me as this means I can't provide a good IPv6 support if it only works on some ports.
Manual:Tools/email - MikroTik Wiki
Secure Email - CheckTLS test how you send email (//email/test From:) test TLS v1.3 email: we use it in and out, and we can test it in and out; test IPv6 email: we use it in and we can test it in and out; test live SPF, DKIM, DMARC; test live MTA-STS, SMTP TLS Reporting, DANE; test and limit to specific TLS versions, cipher suites, etc. (sender and receiver) test Mail Server Test - Check SPF, MX, PTR records and RFC Enter the mail domain you want to check into the Domain name field and hit the "Check!" button. The mail domain is the domain part of an email address. for example if you have an email address email@example.com, then you want to fill in example.com, and not to use any kind of subdomain like www.example.com.However, some emails do have domain part with subdomains, such as …
The SMTP server now requires that IPv6 addresses in SMTP commands are specified as [ipv6:ipv6address], as described in RFC 2821. The IPv6 network address matching code was rewritten from the ground up, and is expected to be closer to the specification. The result may be incompatible with the Postfix/IPv6 patch. IPv6 Support for unsupported
Sep 12, 2014 Check for SMTP TLS from command line with OpenSSL Jun 05, 2014 Solved: Cannot resolve SMTP for Scan to E-mail feature Set up > Network set up > Network services > IPV6 > Off. For gmail you may want to test with the 465 port as well . What worked, was entering the IP address of the SMTP server manually (which, of course, defeats the purpose of having domain names in the first place). Of course, the SMTP port has to be enabled in the firewall. windows server 2008 r2 - SMTP - Remove IPv6? - Server Fault