I think I found one pretty much serious bug... Messages sent via webmail, to external recipients which are having . (dot) in their email, can't be sent when you first push the send button, only on subsequent retries. Here's what I get in web mail, why postfix sometimes rejects messages sent through webmail?

Anyone managed to solve this problem? Or at least make workaround? Thanks!

Message not sent; one or more addresses were not accepted.
Rejected addresses: Coa <xx.xx@ymail.com>
method: [unknown]
msg: Invalid address: Coa <xx.xx@ymail.com>. com.zimbra.cs.mailbox.MailSender$SafeSendFailedExc eption: MESSAGE_NOT_DELIVERED; chained exception is: com.zimbra.cs.mailclient.smtp.InvalidRecipientExce ption: RCPT failed: Invalid recipient xx.xx@ymail.com: 550 Please turn on SMTP Authentication in your mail client, or login to the
detail: soap:Sender
trace: qtp1635701107-140:

Body: {
SendMsgRequest: {
_jsns: "urn:zimbraMail",
m: {
e: [
// [0]:
a: "xx.xx@ymail.com",
p: "Coa",
t: "t"
// [1]:
a: "xx@player.rs",
p: "Proba Probic",
t: "f"
idnt: "f3b09096-812a-4b04-97f6-379242b070ec",
irt: {
_content: "&lt;0A82BA53-713D-4D20-A06C-5457BAF880EE@ymail.com&gt;"
mp: [
// [0]:
ct: "multipart/alternative",
mp: [
// [0]:
content: {
_content: "joj nisam, smaracu te jos