January 2, 2022. I bought an Apple watch SE online. Because it came with a 6000 yen New Year's gift coupon. However, I haven't received the coupon email even after waiting. By the way, I didn't receive an order email.

Watch logs.

Jan  6 10:58:29 localhost postfix/smtpd[266092]: connect from rn2-txn-msbadger07103.apple.com[17.111.110.*]
Jan  6 10:58:29 localhost postfix/smtpd[266092]: Anonymous TLS connection established from rn2-txn-msbadger07103.apple.com[17.111.110.*]: TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)
Jan  6 10:58:30 localhost postfix/smtpd[266092]: 3315F37760: client=rn2-txn-msbadger07103.apple.com[17.111.110.*]
Jan  6 11:03:30 localhost postfix/smtpd[266092]: timeout after DATA (0 bytes) from rn2-txn-msbadger07103.apple.com[17.111.110.*]
Jan  6 11:03:30 localhost postfix/smtpd[266092]: disconnect from rn2-txn-msbadger07103.apple.com[17.111.110.*] ehlo=2 starttls=1 mail=1 rcpt=1 data=0/1 commands=5/6

Exist timeout. 0 bytes ... Googling with "timeout after DATA".

特定のドメインからメールが届かない timeout after DATA from

Try changing the MTU of the mail server (Postfix, Ubuntu20.04 LXD container).

# MTU
ifconfig | grep -i mtu
ifconfig the0 mtu 1452

I was able to receive it properly. Edit netplan to reflect the settings permanently.

The problem becomes clear.

I misconfigured VyOS. No MTU on interfaces eth0 (eth1, eth2,...), MTU on interfaces pppoe pppoe0. Also set MSS in Policy.