Router blocking Port 25 whenever it wants

[CYPER]

So I have TP-Link TD-W8961ND and when I try to send an email with Thunderbird it says the connection to the SMTP server has timed out. Then I restart my router without changing any settings and presto I can send my email. 2 hours later things repeat.

I've tried disabling Firewall and SPI, enabling DMZ, forwarding port 25 inside the router settings - nothing works. Only when I restart it then I can send an email.

Any suggestions?

 

[Skidilliplop]

you shouldn't need to forward any ports for outbound connections. It sounds like the router is crashing/flushing it's sessions table. No one is torrenting or something at the same time are they?