IDLE not working for one account only

[Neil Price]

On 05/06/2018 12:19, Geoff Winkless wrote:
> On Tue, 5 Jun 2018 at 08:17, Neil Price <nprice at gibb.co.za> wrote:
>> I can not see anything the account setup that can cause this, suggestions?
> Running behind an overly-aggressive TCP proxy?
There is no proxy involved. They are all on the same physical network.
> What does tcpdump/wireshark show?
>
What am I looking for? The only thing I see which is relevant after a 
mail has been sent is

12:56:23.475625 IP (tos 0x0, ttl 64, id 34941, offset 0, flags [DF], 
proto TCP (6), length 82)
     ctgw-3.ad.gibb.co.za.imap2 > 192.168.102.228.61763: Flags [P.], 
cksum 0x4cb5 (incorrect -> 0xa2e7), seq 20:62, ack 19, win 229, length 42
12:56:23.475680 IP (tos 0x0, ttl 64, id 34942, offset 0, flags [DF], 
proto TCP (6), length 40)
     ctgw-3.ad.gibb.co.za.imap2 > 192.168.102.228.61763: Flags [F.], 
cksum 0x4c8b (incorrect -> 0x1866), seq 62, ack 19, win 229, length 0
12:56:23.475911 IP (tos 0x0, ttl 127, id 3446, offset 0, flags [DF], 
proto TCP (6), length 40)
     192.168.102.228.61763 > ctgw-3.ad.gibb.co.za.imap2: Flags [.], 
cksum 0x1148 (correct), seq 19, ack 63, win 2051, length 0
12:56:23.476233 IP (tos 0x0, ttl 127, id 3447, offset 0, flags [DF], 
proto TCP (6), length 40)
     192.168.102.228.61763 > ctgw-3.ad.gibb.co.za.imap2: Flags [F.], 
cksum 0x1147 (correct), seq 19, ack 63, win 2051, length 0
12:56:23.476256 IP (tos 0x0, ttl 64, id 6556, offset 0, flags [DF], 
proto TCP (6), length 40)
     ctgw-3.ad.gibb.co.za.imap2 > 192.168.102.228.61763: Flags [.], 
cksum 0x1865 (correct), seq 63, ack 20, win 229, length 0
12:56:23.915208 IP (tos 0x0, ttl 63, id 21520, offset 0, flags [DF], 
proto TCP (6), length 52)
     192.168.102.146.58600 > ctgw-3.ad.gibb.co.za.8008: Flags [.], cksum 
0xea47 (correct), seq 1364296473, ack 954946665, win 245, options 
[nop,nop,TS val 1683933952 ecr
12:56:23.915224 IP (tos 0x0, ttl 64, id 965, offset 0, flags [DF], proto 
TCP (6), length 52)

where ctgw-3.ad.gibb.co.za is the cyrus server and 192.168.102.228 is 
currently the misbehaving client.