Google の古い G-Suite アカウントでユーザー ドメイン エイリアスとして上記を設定しましたが、次の 2 つの警告メッセージが引き続き表示されます。
There were some non-critical problems detected with the configuration of this domain.
Depending on how you configured your mail-flow, this could be a source of mail delivery issues.
DKIM is not set up. warning [this one always appears in yellow]
TXT lookup should fit in one UDP response packet.
https://toolbox.googleapps.com/apps/checkmx/check?domain=webcoder.co.uk
他のツールに従って SPF と DKIM を正しく設定し、DNS に必要なエントリをいくつかだけ検証しました。
# dig webcoder.co.uk any
; <<>> DiG 9.16.1-Ubuntu <<>> webcoder.co.uk any
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 13051
;; flags: qr rd ra; QUERY: 1, ANSWER: 11, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;webcoder.co.uk. IN ANY
;; ANSWER SECTION:
webcoder.co.uk. 86400 IN A 176.58.127.176
webcoder.co.uk. 86400 IN NS ns1.tsodns.com.
webcoder.co.uk. 86400 IN NS ns2.tsodns.com.
webcoder.co.uk. 86400 IN SOA ns1.tsodns.com. support.tsohost.com. 1628681639 10800 3600 604800 3600
webcoder.co.uk. 86400 IN MX 1 ASPMX.L.GOOGLE.com.
webcoder.co.uk. 86400 IN MX 5 ALT1.ASPMX.L.GOOGLE.com.
webcoder.co.uk. 86400 IN MX 5 ALT2.ASPMX.L.GOOGLE.com.
webcoder.co.uk. 86400 IN MX 10 ALT3.ASPMX.L.GOOGLE.com.
webcoder.co.uk. 86400 IN MX 10 ALT4.ASPMX.L.GOOGLE.com.
webcoder.co.uk. 86400 IN TXT "google-site-verification=oYfc0eoSUnoeUBYoTYKS9qIUlUlw6cHk6IWdC4UfTCc"
webcoder.co.uk. 86400 IN TXT "v=spf1 include:_spf.google.com ~all"
;; Query time: 19 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Wed Aug 11 13:00:02 BST 2021
;; MSG SIZE rcvd: 401
# dig webcoder.eu any
; <<>> DiG 9.16.1-Ubuntu <<>> webcoder.eu any
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 63301
;; flags: qr rd ra; QUERY: 1, ANSWER: 12, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;webcoder.eu. IN ANY
;; ANSWER SECTION:
webcoder.eu. 86400 IN A 176.58.127.176
webcoder.eu. 3600 IN NS ns51.domaincontrol.com.
webcoder.eu. 3600 IN NS ns52.domaincontrol.com.
webcoder.eu. 3600 IN SOA ns51.domaincontrol.com. dns.jomax.net. 2021081123 28800 7200 604800 3600
webcoder.eu. 604800 IN MX 20 alt1.aspmx.l.google.com.
webcoder.eu. 604800 IN MX 30 alt2.aspmx.l.google.com.
webcoder.eu. 604800 IN MX 10 aspmx.l.google.com.
webcoder.eu. 604800 IN MX 40 aspmx2.googlemail.com.
webcoder.eu. 604800 IN MX 50 aspmx3.googlemail.com.
webcoder.eu. 86400 IN TXT "v=spf1 include:_spf.google.com ~all"
webcoder.eu. 86400 IN TXT "MS=ms50869792"
webcoder.eu. 86400 IN TXT "google-site-verification=mq-5iDOSGsTY1whcBFqWbq6DXAy9WfD9YpXlDGU3Qyg"
;; Query time: 79 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Wed Aug 11 13:00:50 BST 2021
;; MSG SIZE rcvd: 445
一方、プライマリ ドメイン webcoder.eu を確認すると、正常に検証された (すべて緑色) か、断続的に UDP エラーが表示されます。
error (in red):
MX lookup must fit in one UDP response packet.
Overly large MX response will cause problems for many senders. To avoid this, either decrease the number of MX records or shorten their names
warning appeared only a couple of times (yellow):
DKIM is not set up. warning
TXT lookup should fit in one UDP response packet.