0 ROCK v13 Communication Attachment sporadic issues 4 Devon McCarty posted 2 Years Ago We recently upgraded to ROCK v13 (from v12) and since then we have had some odd issues with communication attachments sporadically working. We have had some emails get sent where the attachments work for some people and not for others. Prior to v13 we did not have this issue. I have explored Mailgun logs for one of the people who sent a communication and their "Test Email" to themself had the attachment listed with a proper size attribute, but when they sent the final communication the log record showed the attachment but the size for it wasn't correct. So, in their email program they could open the attachment for the test email, but not the final communication. Then they received word from some people on that communication that they were able to open the attachment just fine while others were reporting it wasn't working.Now I noticed that with v13 there was this change "Updated communication system and transport to use multiple threads when sending communications and when processing each recipient." A theory I have is, I'm wondering if the multiple threads may not have proper access to the attachment file and that is why it is working for some and not others.Again, we didn't have this issue prior to v13 (we are the latest at the moment, v13.3). Any help would be greatly appreciated.Update: 2022-05-04 at 5pmAfter exploring this a little more in Mailgun, it doesn't appear to be an issue with email hosts. I found two logs with the same mx-host and one had an attachment size of "162" and wasn't able to open the attachment, while another had an attachment size of "404152" and was able to open the attachment. In mailgun, both log entries were the same minute. So my theory still is that one Rock thread could properly send the attachment, while the other for some reason couldn't.Update: 2022-05-07Thank you @Michael Roth for your suggestion to use Mailgun API and @Jonathan Anderson for also verifying this with using SendGrid API. We made the switch from SMTP to the API and haven't had this issue occur.Update: 2022-06-17Notice issued from ROCK for an upcoming change: "Starting in Rock v14.0 the SMTP transport is no longer supported. The newer HTTPS transports, and improvements in the way Rock uses them, have significantly boosted the speed at which messages to a large number of recipients can be sent. The continued use of the SMTP transport works against these performance improvements and has created some reported issues with corrupted attachments. The new transports are very easy to use."