Hi All,

We use stunnel to send emails from our scanners to our hosted mail provider (that now only accept TLS connections).

This has been working well for a number of years, but just recently the scanners (all Lexmark) have sporadically been giving errors of ‘connection failed’.

If I check the stunnel logs, the failed send has an extra line in of TLS socket closed (SSL_write) with 418 unsent byte(s)

Below are 2 examples, 59 was sent successfully, 60 was not.

2018.01.16 14:37:24 LOG5[59]: Service [fasthosts-smtp] accepted connection from 10.226.174.95:11473

2018.01.16 14:37:24 LOG5[59]: s_connect: connected 213.171.216.50:465

2018.01.16 14:37:24 LOG5[59]: Service [fasthosts-smtp] connected remote server from 10.226.150.9:52577

2018.01.16 14:37:24 LOG5[59]: OCSP: Connecting the AIA responder "http://t2.symcb.com"

2018.01.16 14:37:24 LOG5[59]: s_connect: connected 23.55.155.27:80

2018.01.16 14:37:24 LOG5[59]: OCSP: Certificate accepted

2018.01.16 14:37:24 LOG5[59]: OCSP: Connecting the AIA responder "http://tj.symcd.com"

2018.01.16 14:37:25 LOG5[59]: s_connect: connected 23.55.155.27:80

2018.01.16 14:37:25 LOG5[59]: OCSP: Certificate accepted

2018.01.16 14:37:25 LOG5[59]: Certificate accepted at depth=0: C=GB, ST=Gloucestershire, L=Gloucester, O=Fasthosts Internet Limited, OU=NOC, CN=smtp.livemail.co.uk

2018.01.16 14:37:29 LOG5[59]: Connection closed: 167106 byte(s) sent to TLS, 376 byte(s) sent to socket

2018.01.16 14:38:19 LOG5[60]: Service [fasthosts-smtp] accepted connection from 10.226.174.95:11483

2018.01.16 14:38:19 LOG5[60]: s_connect: connected 213.171.216.50:465

2018.01.16 14:38:19 LOG5[60]: Service [fasthosts-smtp] connected remote server from 10.226.150.9:52620

2018.01.16 14:38:19 LOG5[60]: OCSP: Connecting the AIA responder "http://t2.symcb.com"

2018.01.16 14:38:19 LOG5[60]: s_connect: connected 23.55.155.27:80

2018.01.16 14:38:19 LOG5[60]: OCSP: Certificate accepted

2018.01.16 14:38:19 LOG5[60]: OCSP: Connecting the AIA responder "http://tj.symcd.com"

2018.01.16 14:38:19 LOG5[60]: s_connect: connected 23.55.155.27:80

2018.01.16 14:38:19 LOG5[60]: OCSP: Certificate accepted

2018.01.16 14:38:19 LOG5[60]: Certificate accepted at depth=0: C=GB, ST=Gloucestershire, L=Gloucester, O=Fasthosts Internet Limited, OU=NOC, CN=smtp.livemail.co.uk

2018.01.16 14:38:24 LOG3[60]: TLS socket closed (SSL_write) with 418 unsent byte(s)

2018.01.16 14:38:24 LOG5[60]: Connection reset: 964 byte(s) sent to TLS, 392 byte(s) sent to socket

Has anyone come across this before?

Our mail provider has send limits in place of 50 every 10 minutes, but I am confident we are not reaching those amounts.

Any help appreciated.

Regards, Stephen