EDIT - I am investigating that the block may be occuring outside of zoho. I will come back and update when i have further information. Until then, no need for action on this request. Thanks.
I have been troubleshooting for a long time today trying to determine why sending emails is failing for me.
I eventually found that connections from my hosted server to smtppro.zoho.com are blocked.
Is it possible to remove this block or at least have my IP address whitelisted? I am just trying to send occasional notification emails when someone fills out a form on a website.
Connecting from my home workstation (a normal TCP handshake):
No. Time Source Destination Protocol Length Info
379 25.708429699 10.0.0.90 136.143.191.24 TCP 76 50934 → 465 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=1142478572 TSecr=0 WS=128
380 25.733441930 136.143.191.24 10.0.0.90 TCP 76 465 → 50934 [SYN, ACK] Seq=0 Ack=1 Win=28960 Len=0 MSS=1360 SACK_PERM=1 TSval=2692359816 TSecr=1142478572 WS=128
381 25.733488087 10.0.0.90 136.143.191.24 TCP 68 50934 → 465 [ACK] Seq=1 Ack=1 Win=64256 Len=0 TSval=1142478598 TSecr=2692359816
382 25.733637606 10.0.0.90 136.143.191.24 TCP 68 50934 → 465 [FIN, ACK] Seq=1 Ack=1 Win=64256 Len=0 TSval=1142478598 TSecr=2692359816
383 25.762101475 136.143.191.24 10.0.0.90 TCP 68 465 → 50934 [FIN, ACK] Seq=1 Ack=2 Win=29056 Len=0 TSval=2692359846 TSecr=1142478598
384 25.762142404 10.0.0.90 136.143.191.24 TCP 68 50934 → 465 [ACK] Seq=2 Ack=2 Win=64256 Len=0 TSval=1142478626 TSecr=2692359846
1090 79.898483429 10.0.0.90 136.143.191.24 TCP 76 33552 → 466 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=1142532763 TSecr=0 WS=128
Trying to connect from my server (and getting blocked):
6 26.860339694 256.256.256.256 → 136.143.191.24 TCP 74 53810 → 465 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=396614166 TSecr=0 WS=128
7 27.888613692 256.256.256.256 → 136.143.191.24 TCP 74 [TCP Retransmission] 53810 → 465 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=396615194 TSecr=0 WS=128
8 29.968597109 256.256.256.256 → 136.143.191.24 TCP 74 [TCP Retransmission] 53810 → 465 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=396617275 TSecr=0 WS=128
9 32.128551655 256.256.256.256 → 136.143.191.24 TCP 74 [TCP Retransmission] 36834 → 466 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=396619434 TSecr=0 WS=128
10 34.048593949 256.256.256.256 → 136.143.191.24 TCP 74 [TCP Retransmission] 53810 → 465 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=396621354 TSecr=0 WS=128
11 42.368575986 256.256.256.256 → 136.143.191.24 TCP 74 [TCP Retransmission] 53810 → 465 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=396629674 TSecr=0 WS=128
12 59.008528721 256.256.256.256 → 136.143.191.24 TCP 74 [TCP Retransmission] 53810 → 465 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=396646314 TSecr=0 WS=128
13 64.768548757 256.256.256.256 → 136.143.191.24 TCP 74 [TCP Retransmission] 36834 → 466 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=396652074 TSecr=0 WS=128
14 91.648608235 256.256.256.256 → 136.143.191.24 TCP 74 [TCP Retransmission] 53810 → 465 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=396678955 TSecr=0 WS=128
(I substituted in my server's ip address with 256.256.256.256 for privacy, but will gladly share the address with any zoho staff)
Thank you.