Editing Email client (section)

===Port numbers===
Email servers and clients by convention use the [[List of TCP and UDP port numbers|TCP port numbers]] in the following table.  For MSA, IMAP and POP3, the table reports also the labels that a client can use to query the [[SRV record]]s and discover both the host name and the port number of the corresponding service.<ref>{{cite IETF |title=Use of SRV Records for Locating Email Submission/Access Services |rfc=6186 |author=Cyrus Daboo |date=March 2011 |publisher=[[Internet Engineering Task Force|IETF]] |access-date=17 April 2013}}</ref>
{| class="wikitable"
|-
! Protocol
! Use
! Plain text or <br>encrypt sessions
! Plain text <br>sessions only
! Encrypt sessions <br>only
|-
| [[Post Office Protocol|POP3]]
| incoming mail
| style="text-align: right;" | 110 <br>_pop3._tcp
|
| style="text-align: right;" | 995 <br>_pop3s._tcp
|-
| [[Internet Message Access Protocol|IMAP4]]
| incoming mail
| style="text-align: right;" | 143 <br>_imap._tcp
|
| style="text-align: right;" | 993 <br>_imaps._tcp
|-
| [[Simple Mail Transfer Protocol|SMTP]]
| outgoing mail
| style="text-align: right;" | 25
|
|style="text-align: right;" |587
|-
| [[Mail submission agent|MSA]]
| outgoing mail
| style="text-align: right;" | 587 <br>_submission._tcp
|
| style="text-align: right;" | 465<ref>{{cite IETF |title=Cleartext Considered Obsolete: Use of Transport Layer Security (TLS) for Email Submission and Access |rfc=8314 |author1=Keith Moore |author2=Chris Newman |date=January 2018 |publisher=[[Internet Engineering Task Force|IETF]] |access-date=12 February 2018}}</ref> <br>_submissions._tcp
|-
| [[HTTP]]
| webmail
|
| style="text-align: right;" | 80
| style="text-align: right;" | 443
|}

While webmail obeys the earlier HTTP disposition of having separate ports for encrypt and plain text sessions, mail protocols use the [[STARTTLS]] technique, thereby allowing encryption to start on an already established TCP connection. While {{IETF RFC|2595}} used to discourage the use of the previously established ports 995 and 993, {{IETF RFC|8314}} promotes the use of implicit [[Transport Layer Security|TLS]] when available.