Thanks Jepping for the reply. Here is a copy of my mail settings. My limit for message size is 100Mb. The file sizes for the pdf are not too big 10-15mb, however the page count is 200-300.
mail:postfix:smtpd_pw_server_security_options:_array_index:0 = "cram-md5"
mail:postfix:smtpd_pw_server_security_options:_array_index:1 = "digest-md5"
mail:postfix:smtpd_pw_server_security_options:_array_index:2 = "gssapi"
mail:postfix:smtpd_pw_server_security_options:_array_index:3 = "login"
mail:postfix:smtpd_pw_server_security_options:_array_index:4 = "plain"
mail:postfix:spam_quarantine = "junk-quarantine@example.com"
mail:postfix:mail_events_log_level = "info"
mail:postfix:smtp_reject_list_enabled = no
mail:postfix:smtp_tls_cert_file = "/etc/certificates/mail.mydomain.com.A58CEC4AA0A3E18FA9EC9576AF7742E60CA039D6.c ert.pem"
mail:postfix:smtp_sasl_auth_enable = no
mail:postfix:whitelist_from = _empty_array
mail:postfix:submit_cred:mail.mydomain.com:username = "submit"
mail:postfix:submit_cred:mail.mydomain.com:password = "KsueIoRDdXSVNCNkq6gwdD"
mail:postfix:submit_cred:FBSAdmins-Mac-mini.local:username = "submit"
mail:postfix:submit_cred:FBSAdmins-Mac-mini.local:password = "KsueIoRDdXSVNCNkq6gwdD"
mail:postfix:smtp_auth_relay_dict:smtp_auth_relay_host = ""
mail:postfix:smtp_auth_relay_dict:smtp_auth_relay_pwd = ""
mail:postfix:smtp_auth_relay_dict:smtp_auth_relay_userid = ""
mail:postfix:client_permit_mynetworks = yes
mail:postfix:smtpd_tls_cert_file = "/etc/certificates/mail.mydomain.com.A58CEC4AA0A3E18FA9EC9576AF7742E60CA039D6.c ert.pem"
mail:postfix:maps_rbl_domains_enabled = yes
mail:postfix:spam_subject_tag = "***JUNK MAIL*** "
mail:postfix:smtpd_tls_CAfile = "/etc/certificates/mail.mydomain.com.A58CEC4AA0A3E18FA9EC9576AF7742E60CA039D6.c hain.pem"
mail:postfix:message_size_limit_enabled = yes
mail:postfix:virus_db_last_update = "2015-04-18 15:04:19 +0000"
mail:postfix:smtp_tls_key_file = "/etc/certificates/mail.mydomain.com.A58CEC4AA0A3E18FA9EC9576AF7742E60CA039D6.k ey.pem"
mail:postfix:mail_enabled_groups:_array_index:0 = "1"
mail:postfix:mail_enabled_groups:_array_index:1 = "2"
mail:postfix:mail_enabled_groups:_array_index:2 = "3"
mail:postfix:mail_enabled_groups:_array_index:3 = "4"
mail:postfix:mail_enabled_groups:_array_index:4 = "5"
mail:postfix:mail_enabled_groups:_array_index:5 = "6"
mail:postfix:mail_enabled_groups:_array_index:6 = "7"
mail:postfix:mail_enabled_groups:_array_index:7 = "8"
mail:postfix:mail_enabled_groups:_array_index:8 = "9"
mail:postfix:mail_enabled_groups:_array_index:9 = "10"
mail:postfix:mail_enabled_groups:_array_index:10 = "11"
mail:postfix:mail_enabled_groups:_array_index:11 = "12"
mail:postfix:mail_enabled_groups:_array_index:12 = "13"
mail:postfix:mail_enabled_groups:_array_index:13 = "14"
mail:postfix:mail_enabled_groups:_array_index:14 = "15"
mail:postfix:mail_enabled_groups:_array_index:15 = "16"
mail:postfix:mail_enabled_groups:_array_index:16 = "17"
mail:postfix:mail_enabled_groups:_array_index:17 = "18"
mail:postfix:mail_enabled_groups:_array_index:18 = "19"
mail:postfix:mail_enabled_groups:_array_index:19 = "20"
mail:postfix:mail_enabled_groups:_array_index:20 = "21"
mail:postfix:mail_enabled_groups:_array_index:21 = "22"
mail:postfix:mail_enabled_groups:_array_index:22 = "23"
mail:postfix:mail_enabled_groups:_array_index:23 = "24"
mail:postfix:mail_enabled_groups:_array_index:24 = "25"
mail:postfix:mail_enabled_groups:_array_index:25 = "26"
mail:postfix:mail_enabled_groups:_array_index:26 = "27"
mail:postfix:mail_enabled_groups:_array_index:27 = "28"
mail:postfix:mail_enabled_groups:_array_index:28 = "29"
mail:postfix:mail_enabled_groups:_array_index:29 = "30"
mail:postfix:mail_enabled_groups:_array_index:30 = "31"
mail:postfix:mail_enabled_groups:_array_index:31 = "32"
mail:postfix:mail_enabled_groups:_array_index:32 = "33"
mail:postfix:mail_enabled_groups:_array_index:33 = "34"
mail:postfix:mail_enabled_groups:_array_index:34 = "35"
mail:postfix:add_whitelist_domain = _empty_array
mail:postfix:virus_scan_enabled = yes
mail:postfix:spam_ok_locales = "en"
mail:postfix:spam_notify_admin_email = "junk-admin@example.com"
mail:postfix:black_hole_domains:_array_index:0 = "zen.spamhaus.org"
mail:postfix:virus_db_log_level = "info"
mail:postfix:spam_scan_enabled = yes
mail:postfix:virus_quarantine = "virus-quarantine@example.com"
mail:postfix:reject_unauth_piplining_enabled = no
mail:postfix:blacklist_from = _empty_array
mail:postfix:spam_rewrite_subject = yes
mail:postfix:message_size_limit = 104857600
mail:postfix:mynetworks:_array_index:0 = "127.0.0.0/8"
mail:postfix:mynetworks:_array_index:1 = "10.27.0.0/21"
mail:postfix:mynetworks:_array_index:2 = "10.0.0.0/24"
mail:postfix:mynetworks:_array_index:3 = "10.23.0.0/21"
mail:postfix:virus_log_level = "info"
mail:postfix:host_whitelist = _empty_array
mail:postfix:domains:_array_index:0:name = "mydomain3.com"
mail:postfix:domains:_array_index:0:count = 4
mail:postfix:domains:_array_index:1:name = "mydomain4.com"
mail:postfix:domains:_array_index:1:count = 13
mail:postfix:domains:_array_index:2:name = "mydomain.com"
mail:postfix:domains:_array_index:2:count = 73
mail:postfix:domains:_array_index:3:name = "mydomain5.com"
mail:postfix:domains:_array_index:3:count = 15
mail:postfix:domains:_array_index:4:name = "mydomain2.com"
mail:postfix:domains:_array_index:4:count = 24
mail:postfix:domains:_array_index:5:name = "mydomain6.com"
mail:postfix:domains:_array_index:5:count = 13
mail:postfix:domains:_array_index:6:name = "mydomain7.com"
mail:postfix:domains:_array_index:6:count = 11
mail:postfix:rbl_override_list = _empty_array
mail:postfix:greylist_enabled = yes
mail:postfix:list_server_log_level = "info"
mail:postfix:group_expansion:start_interval = 10
mail:postfix:group_expansion:enable_group_expansion = no
mail:postfix:virus_notify_recipients = no
mail:postfix:luser_relay_enabled = no
mail:postfix:mydomain = "mydomain.com"
mail:postfix:enable_list_server = yes
mail:postfix:mydestination:_array_index:0 = "localhost"
mail:postfix:mydestination:_array_index:1 = "$mydomain"
mail:postfix:virus_notify_admin_email = "virus-admin@example.com"
mail:postfix:enable_virtual_domains = yes
mail:postfix:spam_notify_admin = no
mail:postfix:smtp_tls_security_level = "may"
mail:postfix:required_hits = 6
mail:postfix:add_whitelist_host = _empty_array
mail:postfix:always_bcc_enabled = no
mail:postfix:enable_var_mail = no
mail:postfix:smtpd_tls_key_file = "/etc/certificates/mail.mydomain.com.A58CEC4AA0A3E18FA9EC9576AF7742E60CA039D6.k ey.pem"
mail:postfix:enable_smtp = yes
mail:postfix:relayhost = ""
mail:postfix:mynetworks_enabled = yes
mail:postfix:require_virtual_map = yes
mail:postfix:spam_ok_languages = "en fr de ja sw ta"
mail:postfix:rbl_override_enabled = no
mail:postfix:log_rolling_days = 1
mail:postfix:enable_smtp_in = yes
mail:postfix:tls_server_options = "require"
mail:postfix:spam_action = "deliver"
mail:postfix:log_rolling_days_enabled = yes
mail:postfix:smtpd_require_virtual_alias_map = no
mail:postfix:spam_log_level = "warn"
mail:postfix:smtp_uce_controlls = 1
mail:postfix:list_server_post_to_archve = no
mail:postfix:relayhost_enabled = no
mail:postfix:list_server_share_archives = no
mail:postfix:virus_action = "delete"
mail:postfix:virus_db_update_days = 12
mail:postfix:smtp_tls_CAfile = "/etc/certificates/mail.mydomain.com.A58CEC4AA0A3E18FA9EC9576AF7742E60CA039D6.c hain.pem"
mail:postfix:virus_notify_admin = no
mail:postfix:domain_whitelist = _empty_array
mail:postfix:myhostname = "mail.mydomain.com"
mail:postfix:reject_unknown_client_enabled = no
mail:postfix:enable_smtp_out = yes
mail:postfix:text_only_attachments = yes
mail:postfix:log_level = "info"
mail:global:skip_enable_service_check = no
mail:global:auto_auth = yes
mail:global:service_data_path = "/Library/Server/Mail"
mail:imap:aps_topic = "com.apple.mail.XServer.af785e7e-febb-41f5-aa7c-8c5e41709220"
mail:imap:servername = ""
mail:imap:imap_auth_clear = yes
mail:imap:auth_gssapi_hostname = ""$ALL""
mail:imap:lmtp_luser_relay_enabled = no
mail:imap:lmtp_luser_relay = ""
mail:imap:push_notify_log_level = "info"
mail:imap:pop_auth_clear = yes
mail:imap:enable_listid_autosave = "no"
mail:imap:max_imap_connections = 1000
mail:imap:log_level = "info"
mail:imap:tls_key_file = "/etc/certificates/mail.mydomain.com.A58CEC4AA0A3E18FA9EC9576AF7742E60CA039D6.k ey.pem"
mail:imap:imap_auth_plain = yes
mail:imap:postmaster_address = "postmaster@mail.mydomain.com"
mail:imap:quotawarn = 80
mail:imap:enable_quota_warnings = yes
mail:imap:pop_auth_gssapi = yes
mail:imap:junk_mail_userid = "junkmail"
mail:imap:global_quota = 0
mail:imap:partitions = _empty_array
mail:imap:tls_ca_file = "/etc/certificates/mail.mydomain.com.A58CEC4AA0A3E18FA9EC9576AF7742E60CA039D6.c hain.pem"
mail:imap:enforce_quotas = yes
mail:imap:not_junk_mail_userid = "notjunkmail"
mail:imap:imap_auth_digest_md5 = yes
mail:imap:request_enable_webmail = no
mail:imap:client_cert_enabled = no
mail:imap:aps_topic_enabled = yes
mail:imap:imap_auth_gssapi = yes
mail:imap:tls_server_options = "require"
mail:imap:pop_auth_apop = yes
mail:imap:quota_full_tempfail = yes
mail:imap:imap_urlauth_host = " "
mail:imap:enable_imap = yes
mail:imap:enable_pop = yes
mail:imap:partition-default = "/Library/Server/Mail/Data/mail"
mail:imap:imap_auth_login = yes
mail:imap:enable_sieve = yes
mail:imap:imap_auth_cram_md5 = yes
mail:imap:notification_server_enabled = yes
mail:imap:tls_cert_file = "/etc/certificates/mail.mydomain.com.A58CEC4AA0A3E18FA9EC9576AF7742E60CA039D6.c ert.pem"