On Fri, Apr 11, 2014 at 01:09:37PM +0200, Reindl Harald wrote: > interesting, i have until now 3 mail client-IPs triggering that rules on > 993 and 995 one of them is our own external office, the other two are > using AppleMail too > > anybody an idea why Mail.app is using Heartbeat packets on POP3s and > IMAPs?
No idea on pop3. But a long-lived imap4 connection waiting in IDLE may cause a stateful firewall (such as common consumer NAT routers) to time-out a connection as "inactive" after a while. That might result in apparently hung connections or otherwise unreliable services. TLS heartbeats would be a convenient way to keep the connection alive through such firewalls and provide a more reliable service to users. Thanks
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