I have a client trying to sending e-mails from an Outlook Distributionlist. But it won't send. The client has tried to cut the list down to make it send - so it is about 70 addresses... All I can see in the mail.log is that imapd has timed out on this client... May 4 20:47:35 server imapd: TIMEOUT, user=xxxxxxxxx, ip=[::ffff:xx.xx.xx.xx], headers=0, body=108648, rcvd=9024, sent=2217533, time=4291 May 4 20:47:51 server imapd: TIMEOUT, user=xxxxxxxxx, ip=[::ffff:xx.xx.xx.xx], headers=0, body=0, rcvd=4931, sent=666235, time=1821 May 4 20:47:51 server imapd: TIMEOUT, user=xxxxxxxxx, ip=[::ffff:xx.xx.xx.xx], headers=0, body=0, rcvd=46, sent=2223, time=1821 ----- I have gotten some more feedback from the client and the error code from Outlook is 0x800CCC0F And from Postfix: 554 Disabled ----- OUTBOX_MULTIPLE_SEND=0 to OUTBOX_MULTIPLE_SEND=1 Without any luck. ----- Yet another update: 1) 554 is an error code that Postfix is giving. 2) Run postconf -d and check the default settings 3) Find smtp_destination_recipient_limit (which is usually set to default_destination_recipient_limit 3a) Default is 50, change this to any number that fits you... e.g. 300 Update: Still the same error message from client.