smtp fails over gateway WAN or VPN

[4o4rh]

The issue I describe started occurring last week, before on 2.4.5p1 before I upgraded to 2.5.0 (which went flawlessly). The issue is still occurring and is a major problem.

Issue
Ubuntu PC

1. Able to send mail through protonmail bridge with no problems.
   Sending through gmail or hotmail accounts via smtp keeps "Socket I/O timeout" errors but is receiving pop mail no problems. packet trace seems to show a lot of Dup Ack
2. Downloading from Yandex suricata is blocking the IPs because of excessive retries. but disabling suricata does not have any effect on above problem

Windows PC

1. Outlook - able to send smtp mail through gmail, but through outlook i receive connection interrupted errors (increasing the timeout hasn't helped)

Android Phone

• doesn't seem to have any problem sending on either gmail or hotmail.

Changed
WAN1 - 120Mg Cable via wifi/modem - configured as modem only (no change)
WAN2 - 100Mg Fibre was connected via fritzbox wifi/switch to cable termination with pfsense network interface igb1 - DHCP * changed * to
pfsense igb1 connected directly to cable termination and PPPoE connection.

Default gateway is WAN2, with each rule specifying a gateway group with WAN2 - Tier 1, WAN1 - Tier 2, member down on both.

Could really use some help on debugging what could have happened. ** i can't be sure the above change had anything to do with this as mrs reports the windows machines were playing up last week, but the ubuntu only started in the last days.

[4o4rh]

@gwaitsi I restored the config with the fritzbox between the fibre and still have the issue with gmail, yandex, etc.

I can see from a packet trace on port 587 it is just full of TCP retransmission errors

[4o4rh]

@gwaitsi well, i got to the root of the problem but don't know how to solve.

If I set the GW to WAN1 or WAN2, smtp is working.

If I set the GW to WAN_GW or VPN_FW it is not working.
This is true whether i put the WAN1/2 hard down.

So something with using the gateway group is killing my smtp on certain clients.

Have no clue on how to solve, everything else seems to work.