What Mikrotik device are you using?

Note that performing a DNS query to see if the hostname needs updated is in breach of Dyn's policies , as is using checkip.dyndns.org every minute: Unacceptable Client Behavior * Send requests to or access anything other than /nic/update at the host members.dyndns.org. * Reverse engineer web request...

I've got 4.16 on mine and don't have a problem - I can max out my 50 Mb/s link no problem at all.

There have been a few threads on the pfSense forum discussing pfSense vs RouterOS. My take (having used both) is that: pfSense runs only on commodity hardware and is more extendible than RouterOS RouterOS runs on (much) lower cost hardware for equivalent performance I'd say that you're better of wit...

Ah. In that case the initial figure you're referring to may instead refer to the overall link speed, not the actual traffic level. Getting a lower level of actual throughput is to be expected.

It probably means you're getting approximately 26 Mb/s (Megabits per second - about 3.3 Megabytes per second) of traffic to/from that host.

Changing your DNS servers won't make any difference to your ability (or not) to stream media (at least not in terms of sustained bandwidth).

Using the 4.0 Beta of Dude I can happily launch Winbox when I use my Windows 7 Ultimate (64 bit) host. It may be an issue with Dude 3?

Yes - as has been said by myself and mrz - block 25/TCP (SMTP) for all except your mail server. Your clients will then have to relay their email through your mail server, where you can apply filtering.

Other than blocking port 25/TCP for anything other than your SMTP server (if you run one) there isn't anything you can do on the RouterOS box itself. If you have your own mail server then you can use one of the many anti-spam engines (commercial or free) to filter out spam and other malicious emails.

mrz, I assume you meant SMTP server?

sir, what are you trying to achieve? Controlling inbound spam to your mail server, outbound spam from your network or outbound spam from your mailserver?

Note that with cable networks in particular you may have to power down the ISP provided device before swapping connected devices. Many cable modems in particular are configured to only allow access to the first device (by MAC address) connected to them after power up.

Have you configured the interface to use a dynamic IP (which includes the netmask and route)? Check the settings for dhcp-client.

Windows Remote Desktop is 3389/TCP

Are these "real" IPs allocated to you, or are you just using them?