opscenter not sending email alerts with AWS-SES

we're running DSE 4.6.5 in a cluster of 4 nodes (m2.4xlarge all in us-east-1) and opscenter 5.1.1 running in a separate server.

we configured email.conf with the credentials of AWS' SES, which we currently use as SMTP for pretty much all of our services (and it works great).

we get emails all the time from opscenter with errors from the repair service or backup failed or stuff like that, but we are NOT getting any email alerts from the configured alerts in opscenter (node down, cluster out of balance and disk %).

in opscenter UI i can see the alert, and i found it is fired in the opscenter logs, but no email goes out (for this case).

the only thing i found in the logs is that it gets timeout while trying to send emails:

2015-04-21 14:31:06+0000 [] INFO: Starting factory <twisted.mail.smtp.ESMTPSenderFactory instance at 0x4a45050>
2015-04-21 14:31:16+0000 [] INFO: SMTP Client retrying server. Retry: 5
2015-04-21 14:31:26+0000 [] INFO: SMTP Client retrying server. Retry: 4
2015-04-21 14:31:36+0000 [] INFO: SMTP Client retrying server. Retry: 3
2015-04-21 14:31:46+0000 [] INFO: SMTP Client retrying server. Retry: 2
2015-04-21 14:31:56+0000 [] INFO: SMTP Client retrying server. Retry: 1
2015-04-21 14:32:06+0000 [dse02] ERROR: Timeout waiting for SMTP server response Error sending event to XXXX@XXXX.com via email
2015-04-21 14:32:06+0
000 []  INFO: Stopping factory <twisted.mail.smtp.ESMTPSenderFactory instance at 0x4a45050>

any ideas?