Email configuration
See post
Setup SPF, DKIM, DMARC
See post
DKIM
generate dkim record for domain
/opt/zimbra/libexec/zmdkimkeyutil -a -d ditsi.ru
add TXT record for your DOMAIN:
Name: d1bc0820-43cd-43e8-b2344-f28asdasb2b9._domainkey
Content: v=DKIM1;k=rsa;p=CAQ8AMI..ManySymbols..IDAQAB
check TXT record
host -t txt D34334-2745-13CA-ABCD-2124ABCDEF._domainkey.domain.net
You can test it here