| 25 | SMTP smtp | TCP UDP | 4/10 moderate | optional |
| 110 | POP3 pop3 | TCP UDP | 6/10 high | optional |
| 995 | POP3S pop3s | TCP UDP | 3/10 moderate | yes |
| 143 | IMAP imap | TCP | 6/10 high | optional |
| 993 | IMAPS imaps | TCP | 3/10 moderate | yes |
| 587 | SMTP submission submission | TCP UDP | 3/10 moderate | optional |
| 465 | SMTPS igmpv3lite, submissions, urd | TCP UDP | 3/10 moderate | yes |
| 50 | Remote Mail Checking Protocol re-mail-ck | TCP UDP | - | - |
| 58 | XNS Mail xns-mail | TCP UDP | - | - |
| 109 | Post Office Protocol - Version 2 pop2 | TCP UDP | - | - |
| 209 | The Quick Mail Transfer Protocol qmtp | TCP UDP | - | - |
| 220 | Interactive Mail Access Protocol v3 imap3 | TCP UDP | - | - |
| 406 | Interactive Mail Support Protocol imsp | TCP UDP | - | - |
| 512 | used by mail system to notify users of new mail received; currently receives messages only from processes on the same machine biff, comsat, exec | UDP TCP | - | - |
| 691 | MS Exchange Routing msexch-routing | TCP UDP | - | - |
| 854 | Dynamic Link Exchange Protocol (DLEP) dlep | TCP UDP | - | - |
| 1143 | Infomatryx Exchange imyx | TCP UDP | - | - |
| 1396 | DVL Active Mail dvl-activemail | TCP UDP | - | - |
| 1397 | Audio Active Mail audio-activmail | TCP UDP | - | - |
| 1398 | Video Active Mail video-activmail | TCP UDP | - | - |
| 1556 | VERITAS Private Branch Exchange veritas_pbx, veritas-pbx | TCP UDP | - | - |
| 2197 | MNP data exchange mnp-exchange | TCP UDP | - | - |
| 2246 | PacketCable MTA Addr Map pc-mta-addrmap | TCP UDP | - | - |
| 2593 | MNS Mail Notice Service mns-mail | TCP UDP | - | - |
| 3007 | Lotus Mail Tracking Agent Protocol lotusmtap | TCP UDP | - | - |
| 3264 | cc:mail/lotus ccmail | TCP UDP | - | - |
| 3332 | MCS Mail Server mcs-mailsvr | TCP UDP | - | - |
| 3436 | GuardControl Exchange Protocol gc-config | TCP UDP | - | - |
| 3667 | IBM Information Exchange infoexch | TCP UDP | - | - |
| 4190 | ManageSieve Protocol sieve | TCP | - | - |
| 4310 | Mir-RT exchange service mirrtex | TCP UDP | - | - |
| 4405 | ASIGRA Televaulting Message Level Restore service ds-mail | TCP UDP | - | - |
| 4538 | Software Data Exchange Gateway swx-gate | TCP UDP | - | - |
| 4569 | Inter-Asterisk eXchange iax | TCP UDP | - | - |
| 4747 | peer-to-peer file exchange protocol buschtrommel | UDP | - | - |
| 5157 | Mediat Remote Object Exchange mediat | TCP | - | - |
| 5196 | The protocol is used by two programs that exchange "table" data used in the AMPL modeling language ampl-tableproxy | TCP | - | - |
| 5429 | Billing and Accounting System Exchange base | TCP UDP | - | - |
| 5682 | BrightCore control & data transfer exchange brightcore | UDP | - | - |
| 6785 | DGPF Individual Exchange dgpf-exchg | TCP UDP | - | - |
| 7300-7359 | The Swiss Exchange swx | | - | - |
| 9060 | CardWeb request-response I/O exchange CardWeb-IO, CardWeb-RT | TCP UDP | - | - |
| 12000 | IBM Enterprise Extender SNA XID Exchange entextxid | TCP UDP | - | - |
| 19220 | Client Connection Management and Data Exchange Service cora, cora-disc | TCP UDP | - | - |
| 28589 | Building operating system services wide area verified exchange bosswave | TCP | - | - |
| 30939 | Persistent peer-to-peer connections for block propagation, transaction relay, and BFT consensus message exchange. dilithium3 | TCP UDP | - | - |
| 35356 | Gutters Note Exchange guttersnex | TCP | - | - |