cURL error: 56 – OpenSSL SSL_read: SSL_ERROR_SYSCALL, errno 104

[Robert Fellner]

Hey everyone,

I have already been in touch with support and we are working to solve this. However, I’d like to push this out to the community as well and see if others are experiencing this.

In a nutshell: I am using Newsletter plugin + Sendgrid essentials to send 100k emails per month. This worked fine and errorfree since a long time. I’ve sent 2,124,138 emails and only had 3 errors.

This changed recently. With the last newsletter I’ve had more than 100 errors and I get the error message:

sendgrid-mailer:
29-09-2023 03:36:36 – FATAL – 7.9.4 – 80.4 MB/8 GB – [cron] > cURL error: 56 – OpenSSL SSL_read: SSL_ERROR_SYSCALL, errno 104
29-09-2023 03:36:36 – FATAL – 7.9.4 – 80.4 MB/8 GB – [cron] > Http error 100 –

In addition in the main-log I get:
28-09-2023 22:06:34 – ERROR – 7.9.4 – 80.5 MB/8 GB – [cron] > TNP_Mailer_Message Object

The weird thing is that sendgrid reports that all emails are delivered including the ones marked as error in TNP. I share the report screenshot with my clients (paid newsletter) so it doesn’t look great when there are 100+ errors and since i had hardly any errors in the past I really want to get this fixed.

Do any of you have a similar issue? Did you make progress fixing it?

Things I’ve done (that achieved nothing):
– changed API key
– updated everything again, tables etc.
– checked limits
– went through sender auth and everything related
– got in touch with sendgrid support (said they don’t report this error)

[Author]

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