strange smtp / Mikrotik problem

RouterOS General
1

Hello Experts,

my pcc load balancer was working perfectly last week but i am facing a problem since 3 days, there is an error while sending emails from any client e.g outlook, thunderbird. i am using imap and smtp port 465.
error on outlook " outlook cannot connect to your smtp server "
error on thunderbird " not connected to smtp server "
none of the client can send emails however all the clients are able to receive emails perfectly.
clients are working perfectly when i conenct on to my isp router directly (by bypassing the mikrotik)
my emails are hosted on google. incoming mail “imap.gmail.com” and outgoing “smtp.gmail.com” these all were working smoothly before 3 days.

2

no one is replying me !! WHY??

3

Well, this is a user forum, not a support desk. There is no guaranteed reply.

Try to add this rule to your mangle list and move it to the top:

/ip firewall mangle
add action=change-mss chain=forward new-mss=clamp-to-pmtu passthrough=yes \
    protocol=tcp tcp-flags=syn

Is there any difference?

4

Aaah finally. thanks alot Sir. this resolved my issue. thank you so much

5

When this solves the problem, there is a mistake in the firewall of your user machine and/or of the router.
You should not drop all ICMP packets, not even when “experts” on the internet tell you to do so.
Dropping all ICMP packets is the cause of this problem.