While gmail can be setup within the Seamonkey email client, some may not want to access their gmail account in that manner nor go through the hassle of doing such; in such a case the following included tools may prove useful.

'One click' access to your gmail account is very simple in LXLE Posh.

First right click on any open area in the Seamonkey menubar or the bookmark menu icon and select 'customize' here you will see button you can add or remove to the SeaMonkey menubar. In here you'll see 'Gmail' button, simply drag and drop it where you want it to appear on the seamonkey menubar. Now once you log into gmail you'll have on click access to your inbox.

Second, to send emails either from a webpage or simply by entering the email address manually using gmail is really easy in Posh. If the email address in on the webpage simply select the email address right click on it and select 'Search' then '(G)mailto' once selected the email address will be loaded into a gmail compose message box if you're already logged into Google. You could also enter the email address in the search box in the top right hand corner of the browser and then select the 'search engine' '(G)mailto:' which will do the same thing, load the email address in the 'to:' line of a compose email box in gmail.

Sounds confusing but it isn't..... 

here are links to the two extensions that make it possible to give you a better idea on how to do it... these extension are already included/loaded in seamonkey in lxle posh..

https://addons.mozilla.org/en-US/firefox/addon/gmail-one-click-login/

https://addons.mozilla.org/en-US/seamonkey/addon/gmailto/