If you find in your apache error logs some lines with:

No space left on device. Couldn't create accept lock

and a normal service restart does not help it has likely something to do with Semaphores running out.

Try a service shutdown and check your apache semaphores afterwards with:
# ipcs | grep apache

Should there still be a lot of them you can delete them with following command:
# ipcs -s | grep apache | perl -e 'while (<STDIN>) { @a=split(/\s+/); print `ipcrm sem $a[1]`}'

Now start your apache normally and verify the logs if the problem has gone.

Hi, enabling TLS on your postfix server is quite simple. Only enable it using following lines in your main.cf config file (usually /etc/postfix/main.cf):

• smtpd_use_tls = yes (enable the TLS usage)
• smtpd_tls_cert_file = /etc/pki/tls/certs/yourcertificate.crt (set your server certificate file)
• smtpd_tls_key_file = /etc/pki/tls/private/yourkey.key (set your server key file)
• smtpd_tls_loglevel = 1 (enable TLS logging*)
• smtpd_tls_security = may (set TLS security level*)
• smtpd_tls_received_header = yes (write TLS status to email header)

​*) TLS logging:
this setting's values are different in postfix v2.9 and later. for example in postfix 2.9+ the TLS handshake is logged even if the value is 0. On the other hand you need to set the value to 1 in postfix earlier to 2.9.

*) TLS security level:
may – if there is an encryption available it will be used
encrypt – means enforce the encryption. Any connection without TLS is refused

you can find more infos on the postfix website.